Chapter VI: Part 6

_Trionyx muticus_ Lesueur, Mém. Mus. Hist. Nat. Paris, 15:263,
pl.7, December, 1827.

_Trionyx muticus muticus_ Webb, Publ. Mus. Nat. Hist. Univ. Kansas,
11:520, August 14, 1959.

_Potamochelys? microcephala_ Gray, Proc. Zool. Soc. London, p. 87,
1864.

_Type._--Lectotype, Museum d'Histoire Naturelle, Paris, No. 8813; dried carapace and plastron; obtained from the Wabash River, New Harmony, Posey County, Indiana, by C. A. Lesueur in August, 1827 (Pl. 53).

_Range._--Central United States; in the Mississippi River drainage from extreme western Pennsylvania, southern Minnesota and South Dakota south to Tennessee, Louisiana and Oklahoma; streams of the Gulf Coast drainage from the Mississippi River in Louisiana westward into Texas including the Colorado River drainage (see map, Fig. 22).

_Diagnosis._--Juvenal pattern of dusky dots and usually short lines or bacilliform marks; ill-defined pale stripes on snout usually evident just in front of eyes; pale postocular stripe lacking thick, black borders that are approximately one-half width of pale stripe (except some in the Colorado River drainage of Texas).

_Description._--Plastral length of smallest hatchling, 2.1 centimeters (INHS 3458); of largest male, 14.0 centimeters (CNHM 92003); of largest female, 21.5 centimeters (KU 2308).

Juvenal pattern of dusky, grayish marks lacking sharp margins, and usually consisting of both small spots and short streaks or dashes, the former predominating; short streaks or dashes occasionally lacking (TU 14375, Pl. 45, bottom, left; UMMZ 92751); markings variable in number, few and widely spaced, or several and closely approximated (Pl. 45, top, topotypes); pale rim separated from ground color by ill-defined, dusky margin; pattern on adult males well-defined resembling that of hatchlings (TU 16172.1, 16173), scarcely discernable (TU 13294), or absent (TU 1242); mottled and blotched pattern on carapace usually contrasting in large females.

Pale stripes extending forward from eyes usually not more than half distance to tip of snout; inner borders of pale stripes on snout usually absent or dusky and indistinct, occasionally blackish (TU 14606); outer borders of pale stripes darker than inner borders, usually blackish; pale stripes on snout occasionally absent (CNHM 7845, UMMZ 92665, TU 5989, none of these specimens being large females); pale postocular stripe having narrow, dusky or blackish borders (especially UMMZ 92751, TU 14436); pale postocular stripe usually complete, occasionally interrupted having prominent dark-bordered anterior segment just behind eye (TU 14416); lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body not contrasting, composed of closely approximated fine markings that are little darker than background, over-all coloration pale grayish; occasionally, few larger and more contrasting markings on hind limbs (UMMZ 92751, TU 14436).

Underparts white, usually lacking markings; occasional dusky markings on plastral area (UMMZ 110502), dark spots or flecks on undersurface of carapace (BCB 6043, UMMZ 92666), or markings on throat (UMMZ 95032).

Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles (Fig. 8g).

_Variation._--Short dusky lines and streaks seem to be lacking from the juvenal pattern on the carapace more often in southern populations (Gulf Coast drainage of Texas) than in northern populations (Mississippi River drainage). I have seen one female, KU 48229 (Pl. 46, bottom, left), plastral length 14.5 centimeters that retained a well-defined juvenal pattern, and lacked a mottled and blotched pattern.

Color notes from life of 11 turtles, KU 55296-306, (eight adult males, three immature females) from the Kansas River at Lawrence, Douglas County, Kansas, are: Buff-yellow rim of carapace, sometimes having pale orange tinge; dusky, dark brown markings on pale brown or tannish carapace of males; dark and pale brown mottled and blotched pattern on carapace of females (smallest specimens having plastral length, 11.0 cm.), many having orangish or buffy hue; soft parts of body brownish to olive-green dorsally, many having small, blackish marks on hind limbs; webbing of limbs yellowish; pale orange, some yellow, laterally at juncture of dark dorsum and pale ventrum (to a lesser extent on hind limbs); pale orange in some suffusing onto dorsal surface of soft parts of body; black-bordered postocular stripes in males having orangish tinge (pattern somewhat obscured in females); whitish ventral surface in some having pale orangish tinge here and there; many having dusky, grayish flecking on plastral area and anterior ventral surface (most intense on 55306 giving appearance of grayish suffusion).

I have seen only three specimens from the Colorado River drainage in Texas. Two of these (UMMZ 92751, TU 14436) are characterized by much black pigmentation. A contrasting pattern of relatively large black marks occurs on the dorsal surface of the soft parts of the body, especially on the hind limbs, and the pale postocular stripes have thick black borders. UMMZ 92751, having a plastral length of 5.5 centimeters, has a juvenal pattern of widely-spaced dark dots that lacks short lines. The other _muticus_ from the Colorado River (CM 3055), a large female 19.0 centimeters in plastral length, has ill-defined postocular stripes lacking dark borders, although a small dusky blotch occurs on the right side of the head.

_Comparisons._--_T. m. muticus_ differs from _T. m. calvatus_ in having pale stripes on the snout, a juvenal pattern of small dusky spots (usually lacking ocellate spots) and short lines, and a pale postocular stripe lacking thick, blackish borders (except in some turtles from the Colorado River system of Texas). One unique characteristic of _muticus_ is the short, dusky lines in the juvenal pattern; these marks, however, are occasionally absent.

_Remarks._--_Trionyx muticus_ generally has been considered a distinct species since its description by Lesueur (1827:263-66, Pl. 7); Wied-Neuwied (1865:53), at least, questioned the identity of _muticus_, believing it to be based on a secondary sexual difference of _T. spiniferus_. Lesueur did not designate a type in the description, and mentioned that he had seen only three specimens (_op. cit._:264). Stejneger (1944:17-18) discussed two mounted specimens (Nos. 787 and 788) in the Natural History Museum at Paris, and mentioned that No. 787 was designated "... as the type on the printed label (although presumably not done by Lesueur)." Dr. Jean Guibé (_in litt._ September 24, 1959) informed me that Nos. 787 and 788 are numbers without value and correspond, respectively, to catalog numbers 8813 and 8814. In addition, the Museum possesses an alcoholic specimen, No. 564, obtained by Lesueur from the Wabash River, that seems to have been acquired by the museum after the publication of the original description. No. 8813 is regarded as a lectotype.

Gray (1864:87) described the species _microcephalus_ and questionably included it in the genus _Potamochelys_ Fitzinger, 1843; the locality was stated as "Sarawak (Wallace)." Gray especially noted the small elongate head and believed that the acquisition of adult specimens would prove that it belonged to a new genus. Later, Gray (1869:221) proposed the generic name _Callinia_ as a new name for _Aspidonectes_ as understood by Agassiz (1857:403). Gray referred _microcephala_ to _Callinia_ (_op. cit._:214, 222) and recognized also _Amyda mutica_ (_op. cit._:212). Baur (1888:1121) remarked that "_Callinia microcephala_ Gray, of the British Museum, with the locality Sarawak, is _Amyda mutica_ Les." The species _microcephalus_ has since been considered a synonym of _Trionyx muticus_. Schmidt (1953:110) designated the type locality as New Harmony, Indiana.

Müller (1878:641) listed the species _Trionyx muticus_ from México as follows: "*b. in Alcohol. Mexico. 1872. [2]." Smith and Taylor (1950:18, footnote) wrote that the record required confirmation. Webb and Legler (1960:24) questionably referred this record to the synonomy of _T. ater_, which resembles _muticus_. _T. muticus_ is not known to occur in México. According to Dr. Lothar Forcart (_in litt._) of the Naturhistorische Museum in Basel, Switzerland, only one specimen on which Müller based his record is extant. My examination of this specimen reveals that it is a hatchling _T. s. emoryi_, plastral length 3.5 centimeters, bearing catalog number 1032; there are no additional data of collection.

Strecker and Williams (1927:16) mentioned one specimen of _muticus_ that was obtained at Christoval, Tom Green County, Texas, and I presume this is the basis for Pope's mention of this species from Tom Green County, Texas (1949:319). Although I do not doubt that _T. muticus_ occurs in Tom Green County, this record possibly is based on _T. spinifer_ because, 1) there are no specimens of _muticus_ in the Strecker Museum from Tom Green County, but there is one specimen of _spinifer_ (SM 3282), and in none of Strecker's publications is there any mention of _spinifer_ from Tom Green County, and 2) Strecker had, at least once, misidentified the two species; his record of _muticus_ from Wallace Bayou, Louisiana (Strecker and Frierson, 1926:last page, no numbers), represents _T. spinifer pallidus_ (SM 2374-75).

_Specimens examined._--Total 261, as follows: ALABAMA: _County unknown_: USNM 118167, Wheeler Reservoir, Tennessee River.

ARKANSAS: _Franklin_: KU 19459-60, Ozark. _Lafayette_: KU 2938, 3057, Lewisville. _Lawrence_: CNHM 92003, Imboden; CNHM 92005, Powhatan; USNM 59214, Black River, Black Rock. _Marion_: TU 14606 (2), White River at Cotter. _Prairie_: KU 1831, 1868, 1870, 1874-76, 1930-31, 1957-63, 2294-302, 2305-06, 2308-09, 2838-41, 3002, White River, DeVall's Bluff.

KANSAS: _Barber_: USNM 95185-86, 1 mi. S Lake City. _Doniphan_: KU 1872, 1878, 1964, Doniphan Lake. _Douglas_: KU 2220, 16148, 23230, 40179, 50825-26, 55296-306, Kansas River, Lawrence; KU 45065-66, 1 mi. N, 1.5 mi. W Lakeview. _Ford_: KU 51516, Ford. _Kearny_: KU 48216, 4 mi. S, 1.5 mi. W Deerfield. _Marshall_: KU 48228, Blue Rapids. _Pottawatomie_: KU 48229-33, 48238, 2 mi. E Manhattan, Riley County. _Reno_: USNM 95260, 6 mi. E Turon. _Riley_: KU 46861, 48234-35, 4 mi. N Manhattan; KU 48236, 2 mi. NE Randolph. _Sedgwick_: UMMZ 95362, Wichita. _Shawnee_: UMMZ 95366-67, Topeka. _Sumner_: USNM 95415, 3 mi. SE Oxford. _Washington_: KU 48237, 8 mi. S Hanover. _Woodson_: KU 45064, 1 mi. E, 2 mi. S Neosho Falls. _County unknown_: USNM 51528.

ILLINOIS: _Cass_: INHS 2146, Beardstown. _Coles_: INHS 1965-67, 3 mi. S Charleston. _Jackson_: INHS 5894, 6.5 mi. N Aldridge, Union County; UMMZ 81570, Mississippi River. _Jasper_: INHS 2412, Rose Hill. _Jersey_: INHS 2156-58, Grafton. _Mason_: INHS 2147, Cedar Creek. _Mercer_: INHS 3458, Keithsburg. _Monroe_: INHS 4088, 3 mi. NE Columbia. _Morgan_: CNHM 6028, INHS 2148, Meredosia. _Pope_: CNHM 2463 (30), Golconda. _Schuyler_: UI 40-41, Crooked Creek. _Shelby_: INHS 2283, Holliday. _Wabash_: INHS 5228, Mt. Carmel.

INDIANA: _Daviess_: UMMZ 110234, White River, 1.5 mi. W Elnora. _Jefferson_: USNM 8337, Madison. _Knox_: UMMZ 111880-81, "near" Decker Chapel. _Posey_: INHS 7278-80, 7447, TTC 798, Wabash River, 2-2.5 mi. S New Harmony; UMMZ 110598, 8 mi. NW Mt. Vernon.

IOWA: _Allamakee_: UMMZ 92657, 1/4 mi. W Victory, Vernon County, Wisconsin; UMMZ 92658-64, Mississippi River, "near" Lansing. _Boon_: UMMZ 92665, Des Moines River at Ledge State Park. _Greene_: UMMZ 92666, 3.5 mi. N Scranton. _Muscatine_: USNM 53521, 54733-34, 54742, 60054-56, Fairport.

LOUISIANA: _Beauregard_: TU 1242, Sabine River, Merryville. _Caddo_: CNHM 7845, Gayles. _Catahoula_: USNM 113228, Jonesville. _Concordia_: USNM 99870, Red River, "near" Shaw. _Ouachita_: TU 5989, Monroe. _Richland_: USNM 100422, Rayville. _Sabine_: TU 13163, 13294, Sabine River, 8 miles SW Negreet. _St. James_: TU 7543, Vacherie. _St. Mar_: USNM 100406, Berwick Bay, "near" Morgan City. _Vernon_: KU 41380, 46777, Sabine River NW Burr Ferry.

MINNESOTA: _Hennepin_: AMNH 4761-62, Fort Snelling.

MISSISSIPPI: _Washington:_ USNM 92605, Greenville. _County unknown_: USNM 115939.

MISSOURI: _Clark_: USNM 59267, 59278, Alexandria. _Daviess_: UMMZ 95505, Grand River, 1 mi. S Jameson. _St. Louis_: SM 2052, St. Louis. _Wayne_: UMMZ 82823, St. Francis River.

NEBRASKA: _Webster_: UMMZ 89526, Republican River, 2 mi. E Inavale.

OKLAHOMA: _Cleveland_: OU 5480-81, 6473, South Canadian River, 4 mi. SE Norman. _Hughes_: KU 50845, 4 mi. N Atwood. _Kay_: OU 9741, 8 mi. E Ponca City. _Le Flore_: OU 2148; OU 27390, Poteau River below Wister Dam. _Love_: OU 27472, Hickory Creek, 9 mi. E Marietta. _Major_: OU 8597, 7 mi. E Orienta. _Marshall_: KU 50827-29, 50848, 50853, OU 27593-94, TU 16077 (4), Lake Texoma, 2 mi. E Willis. _McIntosh_: OU 8993, 4 mi. W Onapa. _Oklahoma_: OU 10137, Lake Oberholser. _Payne_: UMMZ 89629, Cimarron River, 3 mi. E Ripley; UMMZ 90002, 19 mi. SE Stillwater. _Pottawatomie_: OU 25176-83, South Canadian River, 5 mi. SW Shawnee. _Roger Mills_: OU 12472. _Sequoyah_: OU 9006, Illinois River, 2 mi. NE Gore. _Tulsa_: UMMZ 95032 (4), Arkansas River at Tulsa. _Woodward_: CNHM 15472-73; OU 8599-600, 5 mi. E, 1 mi. N Woodward.

SOUTH DAKOTA: _Yankton_: UMMZ 110499-500, Missouri River at Fort Randall; UMMZ 110501-02, Missouri River at Yankton.

TENNESSEE: _Benton_: UMMZ 53198, Trotter's Landing. _Lake_: USNM 102677, Reelfoot Lake. _Obion_: USNM 102910, Reelfoot Lake.

TEXAS: _Archer_: TU 16173, Lake Diversion. _Baylor_: TU 16172 (2), Lake Kemp. _Brazos_: TCWC 7250, Bryan. _Clay_: TCWC 7248-49, 7259-61, 8 mi. NW Ringgold, Montague County; TU 16667, 3 mi. W Byers. _Grayson_: UI 2419, Lake Texoma. _Gregg_: SM 6685, near Gladewater; USNM 22629, Sabine River, 5 mi. S Longview. _Liberty_: TU 14416, 14375, Trinity River, "near" jct. with Big Creek. _McLennan_: BCB 6030, 6043, SM 2557, 2561, Lake Waco. _Matagorda_: CM 3055, Colorado River, Bay City. _San Saba_: TU 14436, San Saba River, 11 mi. NNW San Saba. _Tarrant_: UMMZ 92750, Worth Lake, Fort Worth. _Wharton_: UMMZ 92751, Colorado River, Wharton.

NO DATA: MCZ 1594 (erroneously recorded from Mobile, Alabama); USNM 029261, 59982.

_Records in the literature._--ARKANSAS: _Garland_: Hot Springs (Combs and Hurter _in_ Strecker, 1924:47). _Jefferson_: Pine Bluff. _Pulaski_: Little Rock. _Sebastian_: Fort Smith (Hurter and Strecker, 1909:21).

ILLINOIS: _Adams_: Quincy (Garman _in_ Cahn, 1937:179). _Alexander_: Horseshoe Lake (Cahn, _loc. cit._); Cairo (Garman _in_ Cahn, _loc. cit._). _Carroll_: 5 mi. S Savanna (Stejneger, 1944:24). _Clay_: Louisville. _Clinton_: Carlyle. _Crawford_: Robinson (Cahn, _loc. cit._). _Cumberland_: Embarrass River (Peters, 1942:183). _Fayette_: Vandalia. _Gallatin_: Shawneetown (Cahn, _loc. cit._). _Hancock_: between Warsaw and Hamilton (Stejneger, _op. cit._:23). _Jackson_: Murphysboro. _Jasper_: Newton. _Marion_: Centralia. _Mason_: Havana. _Massac_: symbol on map. _Menard_: Petersburg. _Peoria_: Peoria. _Randolph_: Chester (Cahn, _loc. cit._). _Richland_: Olney (Stejneger, _loc. cit._). _Rock Island_: Rock Island. _St. Clair_: East St. Louis (Cahn, _loc. cit._). _Union_: (Cagle, 1942a:199). _White_: Carmi. _Whiteside_: Sterling (Cahn, _loc. cit._). _Woodford_: Mackinaw Creek (Garman _in_ Cahn, _loc. cit._).

INDIANA: _Carroll_: "near" Delphi (Agassiz, 1857:400). _Vigo_: Terre Haute (Blatchley, 1891:22).

IOWA: _Des Moines_: "near" Burlington (Agassiz, 1857:400). _Dubuque_: Mississippi River, 8 mi. S Dubuque (Goldsmith, 1945:447). _Lee_: Keokuk (Stejneger, 1944:23).

KANSAS: _Barber_: 5 mi. SE Lake City; Salt River, S of Aetna (Burt, 1935:321). _Cowley_: symbols on map (Smith, 1956:157). _Gray_: Arkansas River, 1 mi. W Cimarron (Clarke, 1956:215). _Leavenworth_: Missouri River, Fort Leavenworth (Brumwell, 1951:207-08). _McPherson_: Lindsborg (Breukelman and Smith, 1946:112). _Pratt_: State Fish Hatchery, "near" Pratt (Taylor, 1933:269). _Trego_: Wakeeney (Stejneger, 1944:24).

KENTUCKY: _Fleming_: Fox. _Rowan_: Triplett (Welter and Carr, 1939:130). _County unknown_: Ohio River (Funkhouser, 1925:71).

LOUISIANA: _De Soto_: Bayou Pierre (Strecker and Frierson, 1926:last page, no numbers).

MINNESOTA: _Houston_: Brownsville (Breckenridge, 1944:183). _Winona_: Homer (Stejneger, 1944:23).

MISSISSIPPI: _Warren_: Vicksburg (Cook, 1946:185).

MISSOURI: _Jackson_: Fry's Lake (Anderson, 1942:219). _Jefferson_: Meramec River (Boyer and Heinze, 1934:199). _County unknown_: Osage River (Agassiz, 1857:400).

NEBRASKA: _Franklin_: 1/2 mi. S Franklin; 1 mi. SE Naponee. _Furnas_: 4 mi. E Cambridge. _Lancaster_: Lincoln. _Nemaha_: Peru. _Thayer_: (Hudson, 1942:102). _Thomas_: (Smith, 1958:36).

NEW MEXICO: _San Miguel_: Conchos River above Conchos Dam (Shields and Lindeborg, 1956:120).

OHIO: _Brown_: mouth White Oak Creek, Higginsport. _Muskingum_: "near" Gaysport. _Pike_: Scioto River in Camp Creek, Newton and Scioto Twps.; Pike Lake. _Scioto_: Scioto River in Clay and Rush Twps.; Scioto River, Portsmouth; Scioto River, 3 mi. N Rushtown. _Tuscarawas_: Tuscarawas River, 2 mi. below Gnadenhutten; "near" Winfield. _Washington_: Dam No. 2, Muskingum River, northern edge of Marietta; Ohio River, 4 mi. SE Marietta (Conant, 1951:156, 264).

OKLAHOMA: _Alfalfa_: 6.5 mi. NE Ingersoll. _Comanche_: Camp Boulder, Wichita National Forest (Ortenburger and Freeman, 1930:188). _McCurtain_: _Pushmataha_: (Ortenburger, 1927:100).

PENNSYLVANIA: _Allegheny_: Neville Island, Ohio River below Pittsburgh (Atkinson, 1901:154). _Clarion_: Allegheny River at Foxburg (Netting, 1944:85).

?SOUTH DAKOTA: _County unknown_: Fort Mackenzie, Missouri River, 6-8 mi. below Cedar Island (Stejneger, 1944:15).

TENNESSEE: _Lake_: Mississippi River (Parker, 1948:29). _Pickett_: Obey River at Eagle Creek Ford (Shoup, Peyton and Gentry, 1941:75).

WISCONSIN: _Crawford_: _Pepin_: Mississippi River (Breckenridge, 1944:183; Pope and Dickinson, 1928:82).

=Trionyx muticus calvatus= Webb

Gulf Coast Smooth Softshell

Plate 47

_Trionyx muticus calvatus_ Webb, Univ. Kansas Publ. Mus. Nat.
Hist., 11:519, 1 fig., 2 pls., August 14, 1959.

_Type._--Holotype, UI 31071, hatchling, sex undetermined, alcoholic; obtained from Pearl River, Roses Bluff, 14 miles northeast Jackson, Rankin County, Mississippi, by William F. Childers on August 25, 1952.

_Range._--Southeastern United States from the Florida Parishes of Louisiana eastward to the western end of the panhandle of Florida; rivers of the Gulf Coast drainage from the Escambia River drainage, Florida, westward to Louisiana and Mississippi including the Pearl River drainage. The eastern extent of geographic range is not known (see map, Fig. 22).

_Diagnosis._--Juvenal pattern of large circular spots, often ocellate; no stripes on dorsal surface of snout; pattern on dorsal surface of limbs of fine markings, not in contrast with ground color; pale postocular stripes having thick black borders approximately one half width of pale stripe on adult males.

_Description._--Plastral length of smallest hatchling, 3.0 centimeters (TU 17301); of largest male, 11.8 centimeters (KU 47118); of largest female, 18.0 centimeters (TU 13473).

Juvenal pattern of dusky, circular spots, some ocellate, lacking short lines and streaks; number of spots variable; some spots on carapace of hatchlings may have maximum diameter of three millimeters (TU 17301); pale rim of carapace having dusky, ragged, inner border; juvenal pattern on adult males absent or usually evident, at least posteriorly (TU 17306.1).

Dorsal surface of snout lacking pale stripes just in front of eyes; pale postocular stripe having thick, black borders on adult males, but narrower, dusky or blackish borders on juveniles and large females; lower border of postocular stripe usually in contact with dusky postlabial line; no other markings on side of head; pattern on dorsal surface of soft parts of body of closely approximated, fine markings that are not in contrast with ground color, over-all coloration grayish; occasionally few larger and more contrasting markings, especially on hind limbs and anteriolateral surface of forelimbs.

Underparts whitish, lacking markings, occasional black flecks or dusky marks posteriorly along ventral edge of carapace (TU 17306.3).

Surface of carapace smooth in adult males; large females lacking prominences posteriorly in center of carapace or in nuchal region; anterior edge of carapace smooth in both sexes, but occasionally having regularly spaced furrows or wrinkles on hatchlings.

_Comparisons._--_T. m. calvatus_ can be distinguished from _T. m. muticus_ by the absence of pale stripes on the snout just in front of the eyes, in having pale postocular stripes that have thick, black borders on adult males, and in having a juvenal pattern of large, circular spots that are often ocellate and three millimeters in diameter (no short lines).

_Remarks._--I have not seen specimens of _calvatus_ from the Tombigbee-Alabama river drainage; presumably Cook's record (1946:185) from Lowndes County, Mississippi, represents this subspecies.

It is still not certain that _calvatus_ occurs in streams that drain into Lake Pontchartrain, Louisiana; TU 17236 from the Amite River that lacks a diagnostic character is questionably referred to _calvatus_ (Webb, 1959:524). As mentioned previously _T. s. asper_ shows little evidence of intergradation with _T. spinifer_ in the Mississippi River drainage; _asper_ is present in streams of the Lake Pontchartrain drainage. _T. m. calvatus_ presumably shows a corresponding relationship with _T. m. muticus_ in the Mississippi River drainage. There are no specimens that indicate intergradation between _calvatus_ and _muticus_; _calvatus_ is expected in streams that drain into Lake Pontchartrain, Louisiana. Probably _calvatus_ occurs eastward in the Apalachicola drainage system.

_Specimens examined._--Total, 38 as follows: FLORIDA: _Escambia_: KU 47116, 50852, 50854-55, 50835-36, TU 13473, 16682, 17301, 17302 (2), Escambia River, 2 mi. E, 1 mi. N Century.

LOUISIANA: _East Baton Rouge_: TU 17236, Amite River, "near" Baton Rouge. _Washington_: TU 13795, Bogue Chitto River, Enon; TU 17303 (5), TU 17304 (4), Pearl River, "near" Varnado. _No data_: TU 17305.

MISSISSIPPI: _Lawrence_: KU 47117-19, TU 16956, USNM 7655, Pearl River within 4 mi. of Monticello; TU 17306 (4), Pearl River, 9 mi. S Monticello. _Marion_: USNM 95133-34, Pearl River, Columbia. _Perry_: MSC uncatalogued (3), 3 mi. SE New Augusta. _Rankin_: UI 31071, Pearl River, Roses Bluff, 14 mi. NE Jackson.

_Records in the literature._--MISSISSIPPI: _Forrest_: no data. _Jones_: Crawford Bridge. _Lowndes_: Columbus, Lake Park (Cook, 1946:185).

NATURAL HISTORY

Habitat

Most writers who describe the general habitat of soft-shelled turtles mention large rivers and streams having some current, and large permanent, quiet bodies of water having soft mud or sand bottoms, but note the general avoidance of temporary water. The impermanence of water in the ponds and "charcos" of headwaters of streams may preclude the presence of softshells from these otherwise suitable habitats. Seemingly, soft-shelled turtles are not restricted to particular local situations or microhabitats in a continuous aquatic environment as are some kinds of fish, which seem to be more or less confined to riffle areas or deep holes. Certain activities of softshells such as burying themselves in soft sand in shallow water or seeking crawfish and other food over a gravel-rock substrate or one that is débris-laden, are best carried on in different habitats. Repeated observations of turtles that are probably engaged in a specific activity in a restricted area may lead to erroneous general conclusions regarding the over-all preference for a specific habitat. Perhaps this accounts for Conant's statement (1951:156) that "In the lower portion of the Scioto River [Ohio] it appears that the present species [_muticus_] is abundant while _spinifer_ is almost entirely absent."

Cagle (1954:181) wrote that softshells "inhabit the extreme headwaters and smaller tributaries." Other statements in the literature indicate the variety in kinds of habitat. In Louisiana, Beyer (1900:44) mentioned _spinifer_ as abundant "in all inland waters, preferring, however, such bayous which have sloping and sandy banks upon which they are fond of sunning themselves." Viosca (1923:41) reported soft-shelled turtles as characteristic "of the large silt-bearing rivers ... such as the Pearl, Amite, Mississippi and Atchafalaya." Cagle and Chaney (1950:386) wrote that _spinifer_ in Louisiana was found in greatest abundance in streams having some current, but that individuals were also common in quiet areas; the habitats recorded were: False River--a lake of clear water supporting an abundance of submerged vegetation, the shallow ends having mats of water hyacinth; Lakes Iatt and Bistineau--cypress swamps having clear or muddy water; Caddo Lake--a large lake having a light oil film on the surface of the water, and vegetation toward the shore consisting of cattails, water lilies and water hyacinths, and along the bank of cypress and willow trees; Caddo Lake Spillway--muddy with swift current; Sabine River--swift current, traps set in quieter backwater areas or near cypress logs in river; Lacassine Refuge--traps set in inlets and coves of ship channel having vegetation of water hyacinth, alligator grass, and along bank, saw grass, cypress knees and snags. Stejneger (1944:59) reported _spinifer_ taken in barrow pits in Mississippi.

In Southern Illinois, Cagle (1942:160) recorded _spinifer_ in drainage ditches (normally having several feet of water and a lush growth of aquatic vegetation) that connect inland swamps to the Mississippi flood-plain but dry up periodically, and in Elkville Lake, an artificial lake having much aquatic vegetation in shallow areas (_op. cit._:157). Myers (1927:339) recorded a _spinifer_ from Indiana from a "tiny brook." In east-central Illinois P. W. Smith (1947:39) recorded _spinifer_ in mud-bottomed dredge ditches, lakes, ponds, small streams and rivers, whereas _muticus_ was found to prefer rivers having clean, sandy bottoms and was not taken from lakes or small streams. This restriction in habitat preference of _muticus_ is again emphasized by Smith and Minton (1957:346) who wrote that in Illinois and Indiana, _muticus_ "generally avoids lakes and minor streams." Weed (1923:48), however, recorded _muticus_ (and _spinifer_) from Meredosia Bay, Illinois, presumably a broad, shallow, muddy ox-bow lake of the Illinois River.

In Minnesota, _spinifer_ has been taken from the Mississippi River, which is described as fairly swift having a fluctuating water level, sandy islands, mud banks, a bed of pebbles and large boulders, and abundant crawfish (Breckenridge, 1955:5). In Michigan, Edgren (1942:180) recorded _spinifer_ from a "very small muck-bottomed lake." Evans and Roecker (1951:69) recorded _spinifer_ from Long Point, Lake Ontario, which is a "broad sand spit, straight on the lakeward side but irregular with wet flats and lagoons on the bayside."

In Kansas, Brumwell (1951:207-08) found "mostly young [_muticus_] ... in the old ponds left during flood stages of the Missouri River" ... and _spinifer_ occasionally ... "in the backwaters where stagnant ponds had been formed." In southcentral Kansas, Burt (1935:321) reported _muticus_ from "a sandbar at junction of a small creek and Medicine River" ... and ... a "shallow sand-bottomed, algae-filled pasture streamlet." The same author reported _spinifer_ from a "sand-bottomed prairie streamlet" ... and ... "an alga-filled pool near a stream." Burt (_loc. cit._) remarked that "No ecological differences in general habitat and field behavior of _mutica_ and _spinifer_ are evident in Kansas." Clarke (1958:21) observed _spinifer_ in Long Creek (Osage County, Kansas), which is a winding stream, characterized by numerous deep holes alternating with rocky riffles, and having high and wooded banks, and mostly mud bottom but occasional rock bottom.

Marr (1944:490) mentioned a _spinifer_ that was obtained on the bank of a small, mud-bottomed stream in the Texas panhandle, and Linsdale and Gressitt (1937:222) recorded _spinifer_ from irrigation canals in Baja California.

In southern Florida, _ferox_ occurs in all fresh-water habitats (Duellman and Schwartz, 1958:272). Carr (1940:107) reported _ferox_ as widely distributed in streams, lakes, big springs and canals. Judging from the numbers of turtles, "the larger canals in the Everglades must represent something like an optimum habitat" (Carr, 1952:417). Wright and Funkhouser (1915:119) wrote that in the Okefinokee Swamp, _ferox_ was especially abundant where the water is deep and the bottom soft, and the species was found wherever there were alligators. Deckert (1918:31) wrote that young _ferox_ were taken in springs and brooks near Jacksonville, Florida. Marchand (_in_ Carr, 1952:417-19) observed _ferox_ while water-goggling in Florida and noted that individuals buried themselves in deep water in white sand, mud or bubbling mud-sand springs, sometimes where there was vegetation overhead. Neill (1951:16) collected _ferox_ in marshes, "prairies," flood-plain lakes, lagoons, ox-bow lakes, mangrove swamps, rivers, creeks, calcareous spring runs, man-made lakes and lime sinks. The same author (_loc. cit._) reported taking _agassizi_ (= _asper_) in large muddy rivers, clear "blackwater" streams, calcareous spring runs, creeks, marshes, lagoons, ox-bow lakes, flood-plain lakes, lime sinks, man-made lakes, and smaller ponds. Crenshaw and Hopkins (1955:16), however, stated that in the area where _T. ferox_ and _T. spinifer asper_ overlap, "_asper_ is nearly always an inhabitant of fluviatile situations whereas _ferox_ is equally closely confined to non-fluviatile lakes and ponds"; in the region of sympatry, Schwartz (1956:8) reported _ferox_ from "a moderately fast, blackwater stream [Combahee River, South Carolina]."

Carr (1952:417) wrote that _ferox_ is not uncommon near the mouths of streams in brackish waters, where the tide must occasionally take it to sea, and cited Conant, who told of an individual found at sea in Bahaman waters; Carr (1940:25) listed _ferox_ as occasional in the marine-littoral, mangrove swamps, as did Neill (1951:16). Neill (1958:26-27) mentioned his observance of _ferox_ at the mouth of the Pithlachascotee River, Pasco County, Florida, where the water is sufficiently saline to favor the growth of oysters, and added that commercial fishermen had told him that these turtles are sometimes netted with loggerhead sea turtles (_Caretta_) in the Indian River. Neill (_op. cit._:5-6) also noted the presence of _ferox_ on Meritt Island, which supports an extensive saltwater herpetofauna, off the coast of Brevard County, Florida. Löding (1922:47) recorded _spinifer_ from Fig Island, Mobile County, Alabama, which is probably a marine or brackish water habitat. Cagle and Chaney (1950:386) obtained one _spinifer_ in a brackish marsh of the Sabine Wildlife Refuge, Louisiana; the poor trapping returns here (one _Trionyx_ and one _Pseudemys_ in 408 trap-hours) suggest that fresh-water species are not abundant in brackish habitats. Neill (1958:26-27) has summarized the occurrence of soft-shelled turtles in marine and brackish habitats.

My own observations indicate a variety of habitat preferences; the term "relatively clear" refers to waters in which visibility extends four to six inches below the surface at night using a head-light.

Individuals of _spinifer_ have been taken in large, deep rivers having a moderate to swift current, relatively clear water, mostly sand and clay bottoms, and emergent débris intermittent along the shoreline; the banks may be steep and of mud having a sparse growth of herbs (Black Warrior River, south of Tuscaloosa, Alabama), or of low extensive, sandy bars and beaches (Escambia River, near Century, Florida, Pl. 50, Fig. 1). A juvenile _spinifer_ was taken by hand among rocks in quiet water behind a rocky shoal in the large, deep-channeled Ocmulgee River (near Hawkinsville, Georgia). Several individuals of _spinifer_ were seen in the Flint River (near Bainbridge, Georgia), which had a swift current in a wide, deep channel, sandy or sand-silt banks, few brush piles along shore and many oölitic, submergent snags on an otherwise sandy bottom; the water was exceedingly clear and permitted water-goggling (this habitat has been obliterated by a dam on the Apalachicola River). A large female _spinifer_ was taken on a set line from the bottom of one of several deep holes (approximately seven feet) that were connected by shallow areas or riffles (near headwaters of Escambia River--Escambia Creek, Escambia County, Alabama). Two large females of _spinifer_ (one escaped) were taken on a trotline set in a large, deep, isolated barrow pit near the Escambia River (near Century, Florida); there was no aquatic vegetation, the water was slightly turbid, and the substrate was of a sand-silt or mud.

In Arkansas, _spinifer_ has been taken in large deep rivers having relatively clear water, a moderate current, steep banks four to 15 feet high, and a substrate of mud with few rocks (one taken on trotline, escaped; Black River, near Black Rock, Lawrence County). Two _spinifer_ were taken (trotline and hoop-net) from a smaller (approximately 50 feet wide) turbid river having a swift current, débris along the shoreline, and mud-gravel banks (Petit Jean Creek, Yell County). Several _spinifer_ and _muticus_ were taken from the White River (Marion County) having a sand-gravel or bed rock bottom and clear water; individuals were collected by hand in shallow water (approximately 3-1/2 feet deep) as they lay on the bottom in the main channel where the current was moderate to swift or in a quiet-water side channel having submergent vegetation.

Lake Texoma, an impoundment on the Red River, having a fluctuating water level with no permanent stand of aquatic vegetation, a mud-rock or sand-silt bottom, and turbid water (Pl. 49, Fig. 1) is a suitable habitat for _spinifer_ and _muticus_. _T. spinifer_ is found in large rivers having relatively clear water, moderate currents, emergent logs and débris, and mud or sand banks (Little River, McCurtain County, Oklahoma, Pl. 48, Fig. 1), or small, shallow, turbid creeks having sand-gravel channels of pools connected by riffle areas (Mayhew Creek, Choctaw County, Oklahoma).

Three _spinifer_ were taken from the Llano River (near Llano, Texas) in a period of low water level in hoop-nets set in a large quiet-water pond about four feet deep and having patches of rushes encroaching into the water from the shore. The river bed of sand, gravel and large boulders consisted of narrower, swift-water channels, small pools and riffles, and large ponds.

Individuals of _T. s. emoryi_ have been taken in large ponds having little or no current, turbid, deep water, and clay or sand-gravel banks (Río Purificación, Padilla, Tamaulipas). Two _emoryi_ were collected from a large pond (Río Sabinas, near Sabinas, Coahuila), which was connected to an adjoining one by riffle areas and had little or no current, relatively clear, greenish water, clay or mud banks, a sand-gravel bottom, and was flanked by brush and large cypress trees. A few _emoryi_ were trapped in hoop-nets that were set in the Río Mesquites, a stream in central Coahuila approximately 20 feet wide and six feet deep, flanked by dense stands of _Phragmites_, and having a moderate current, relatively clear, pea-green water and a mud-sand substrate with some gravel; the stream enlarged in some places to form quiet-water coves (Pl. 48, Fig. 2). One adult male _emoryi_ was taken from a crystal-clear, dendritic, pond (El Mojarral, near Cuatro Ciénegas, Coahuila), having shallow areas averaging about two feet but several deep holes--in one of these at the west end of the pond the water was being emitted under pressure from an underwater cavern and "bubbling" at the surface; the vegetation consisted of scattered patches of water-lilies and stonewort; the bottom was a soft mud-marl, and in some places was carpeted with shells of small gastropods. This habitat corresponds to that of the type locality of _T. ater_ (Pl. 49, Fig. 2); see description in Webb and Legler (1960:26). The water of the ponds is warm; at 8 p. m. on July 31, 1959, the temperature of the water at the type locality of _ater_ was 29° C., and the air was 27° C.

An immature female _spinifer_ was taken on a trotline in a swift, clear, cold-water habitat having mud banks and an abundance of brush piles (Little Tennessee River, Monroe County, Tennessee). _T. spinifer_ occurs also in large ox-bow lakes having relatively clear water, extensive mats of submerged vegetation, a soft mud bottom, and several emergent stumps and fallen logs (Lake Concordia, Concordia Parish, Louisiana); alligator grass and cypress trees encroached to the shoreline.

Locality data of some individuals of _spinifer_, _hartwegi_, _asper_, _pallidus_ and _emoryi_ that were examined indicated that turtles were captured in ponds, bayous, sloughs, lakes, impoundments, rivers and creeks, indicating habitation of essentially all permanent waters.

A juvenile of _hartwegi_ was seen by Mr. Wendell L. Minckley on a gravel bar jutting into a small, shallow creek having a mud-gravel bottom (Carnahan Creek, Pottawatomie County, Kansas); the impounding of the Big Blue River by the Turtle Creek Dam will obliterate this habitat. Mr. J. Knox Jones, Jr. reported seeing a large softshell in a narrow, shallow, clear sandy creek in Holt County, Nebraska.

_T. s. emoryi_ occurs in large rivers having generally turbid waters, a moderate to swift current and mud or sand bottoms such as the Río Grande; this habitat corresponds to that of large rivers in the western parts of the range of _T. s. pallidus_ (Red and Washita) and _T. s. hartwegi_ (Canadian and Cimarron). These last-named rivers, in periods of low water level, often have shallow, clear, flowing water in parts of the river bed. _T. s. emoryi_ has also been taken from small creeks having bottoms of rocks and large boulders (Black River Village, Eddy County, New Mexico; field notes of Sydney Anderson and Kenneth Shain, June 12-14, 1958).

I received a hatchling _T. s. guadalupensis_ that was obtained in a clear, shallow-water stream (Hondo Creek, Bandera County, Texas, on April 12, 1958). The larger streams and rivers known to be inhabited by _guadalupensis_ are generally clear having greenish-tinted waters. The geographic distribution of _guadalupensis_ indicates that that subspecies occurs principally in those waters that drain the limestone-mantled, Edward's Plateau off the Balcones Escarpment; the headwaters are characterized by clear, calcareous streams having occasional travertine deposits. It is probably this type of habitat to which Agassiz's statement (1857:408) of "clear, bold and rocky streams" refers.

There are a few specimens whose locality data indicate a tolerance of brackish-water habitats. An adult male _spinifer_ was obtained at Delacroix Island, St. Bernard Parish, Louisiana, a locality said to have exceedingly brackish waters (Dr. George H. Bick, St. Mary's College, Notre Dame, Indiana); this adult male (TU 16170) is unique in having a mottled and blotched pattern. Another adult male (_spinifer_, TU 16071) was obtained in shallow water in Lake Pontchartrain at the mouth of Tchefuncta Creek; the salinity at the time of capture was recorded as 1.7 (datum from Dr. Royal D. Suttkus, Tulane University), indicating only slightly brackish water. Two _spinifer_ (USNM 100409-10) and one _muticus_ (USNM 100406) were taken at Berwick Bay, near Morgan City, St. Mary's Parish, Louisiana; the waters at this locality are probably brackish. The tolerance of brackish waters doubtless facilitates the dispersal of these turtles along coastal marshes and swamps, and into adjacent drainage systems. The greater number of records in the literature pertaining to _ferox_ suggest that this species may be more tolerant of brackish and marine waters than are _spinifer_ or _muticus_.

In summary, _T. ferox_ occurs in all fresh-water habitats, but chiefly in lentic habitats in the northern part of its range where it and _T. s. asper_ are sympatric. _T. ferox_ possibly is more tolerant of brackish and marine waters than are the subspecies of _spinifer_ and _muticus_.

The subspecies of _T. spinifer_ occur in all fresh-water habitats. In the southern part of the geographic range, which overlaps that of _T. ferox_, _T. s. asper_ occurs principally in running-water habitats. _T. s. pallidus_ and _T. s. asper_ are tolerant of brackish-water habitats. _T. s. guadalupensis_, known at present only from rivers and streams, occurs principally in river systems that drain the Edward's Plateau of southcentral Texas. _T. ater_ is confined to crystal-clear ponds in central Coahuila.

The subspecies _muticus_ occurs in large rivers and streams throughout its geographic range, but is known from lakes and impoundments principally in the southern part of its range (the northernmost record is from Reelfoot Lake, Obion County, Tennessee); there is only one record of _muticus_ from a small, shallow, headwater creek (Reno County, Kansas), and only one from a lentic habitat (Meredosia Bay, Illinois) in the northern part of its range. _T. muticus calvatus_ is known at present only from rivers and streams.

The seemingly greater restriction of _muticus_ to running-water habitats suggests less vagility than in _spinifer_ (Netting, 1944:86).

Size and coloration are adaptations to habitat. Soft-shelled turtles of large size are best adapted to mesic, essentially continuous swampy or marshy habitats, whereas small size is an adaptation to less continuous, semi-isolated habitats. A turtle of the maximum size attained by _ferox_ in the habitat of _emoryi_ would, in a general way, probably be more conspicuous and exposed to its enemies, both in the aquatic environment and during overland excursions; perhaps the kind and amount of food would be insufficient. In any event, small size is correlated with the more arid habitats of the southwest, and large size with mesic ones in the southeast. _T. ferox_, the largest species, and the smallest population of _T. spinifer_ (resembling _muticus_) both occur in the southernmost part of the range of the genus. This situation does not support the corollary of Bergmann's Rule, that pertains to some groups of terrestrial reptiles, in which those subspecies occurring farther north, or in cooler climates during their season of activity, tend to be smaller.

Within the species _spinifer_, the _emoryi_ group of subspecies are pallid having whitish dots on the carapace and lack extensive black pigmentation; these features seem to confer protective coloration on the inhabitants of arid, essentially sandy or muddy habitats having sluggish, turbid waters, whereas the more contrasting patterns of the _spinifer_ group of subspecies eastward seem more suited to existence in clearer, swifter waters.

The occurrence of the two clines, _spinifer-hartwegi_ and _pallidus-guadalupensis_, in the species _spinifer_ are notable in that the former occurs mostly in one large continuous drainage system, that of the Mississippi, and shows no sharp break in the one character distinguishing the two subspecies whereas populations composing the _pallidus-guadalupensis_ cline are separated into several river drainages, and show a relatively sharp break in several characters at the Brazos-Colorado river divide. This situation seemingly supports the thesis that clines are maintained by some sort of parallel gradient in ecological or geological conditions. It is notable that streams draining the Edward's Plateau (inhabited by _guadalupensis_) differ in quantity (more) and quality (especially CO_{3}^{--}, Ca^{++}, and Mg^{++} ions) of their solutes, and probably pH (higher) from those farther east (Hubbs, 1957:102). The gross difference in habitats mentioned above (sandy, turbid, sluggish streams in the west _vs._ clear, swift streams in the east) may affect the differentiation recognizable in the _spinifer-hartwegi_ cline.

Daily and Seasonal Activity

_Diurnal Habits_

Softshells bask on débris in the water or on banks close to the water; basking presumably raises the bodily temperature. In general in the southeastern and southwestern United States, I have seen softshells basking only rarely but once saw six at one time close together on logs in Bowie Creek, Hattiesburg, Mississippi (species undetermined). Surface (1908:122) saw _spinifer_ in rows on rocks or logs in tributaries of the Ohio River. Duellman and Schwartz (1958:271-72) stated that _ferox_ basks on banks or beds of aquatic vegetation. Deckert (1918:31) mentioned large _ferox_ "sunning in shallow water at edge of pond." Minton (1944:447) wrote that _muticus_ and _spinifer_ sun on steep mud banks (Wabash River). Cahn (1937:180) stated that _muticus_ (in Illinois) basks on banks at the water's edge but seldom on logs, and suggests that _muticus_ is less prone to leave the water than _spinifer_. According to Carr (1952:438), _muticus_ never basks on logs or rocks. In Ohio, Conant (1951:159) mentioned _spinifer_ as occasionally basking upon a log or rock, or sometimes on steep clay banks of streams. On banks, quick escape is facilitated by directing the head toward the water, thus eliminating the time that it would take to turn around on land (Conant, _loc. cit._; Newman, 1906:129). Evermann and Clark (1920:593) mentioned _spinifer_ as basking on sandy or grassy shores, and large boulders. Muller (1921:181) wrote that _muticus_ basks four to ten feet from the water's edge on gently sloping sand and mud shores of small islands in the Mississippi River (near Fairport, Iowa). Muller stated that basking usually occurs in the morning, up until 2 p. m., and that beaches with a northern exposure were preferred; he observed 37 turtles within a 50-foot stretch of beach. In captivity, hatchlings bask on wire-mesh supports.

I have frequently observed softshells floating at the surface of the water, a habit previously mentioned by Surface (1908:122) and Pope (1949:305, 311). Individuals of _Pseudemys_ and, to a lesser extent, _Graptemys_ also float at the surface; those kinds of turtles and softshells at least, often appear at the surface of the water, seemingly as a result of an inquisitiveness, following repeated disturbances that cause submergence.

Newman (1906:131) described the active pursuit of food: "They crawl or swim along the bottom, thrusting their snouts under stones and into masses of aquatic vegetation, occasionally snapping up a crayfish or larva that they have succeeded in dislodging. They do not tear up their food, but swallow it whole, using the forefeet to assist in forcing it down." Surface (1908:123) suggested that softshells may feed "upon insects which may be found floating on the water," and I have had captives take insects from the surface of the water. Carr (1940:107) also wrote that _ferox_ and numerous gars in the Tamiami Canal, often at the mouths of the tributary ditches, snap at each other furiously as floating bits of food are washed in from the Everglades. Another habit that has been mentioned as an aid in acquiring food (Breckenridge, 1944:186; Conant, 1951:156; Hudson, 1942:101) is burrowing just below the surface in a soft bottom in shallow water, to ambush passing fish, or other food. Presumably all kinds of softshells do this in both shallow and deep water of lakes or rivers having a suitable substrate; _spinifer_ and _muticus_ have been reported to burrow in shallow waters (no observations in deep water) by Agassiz (1857:333), Cahn (1937:180, 189), Conant (1951:159) and Weed (1923:48). Marchand (_in_ Carr, 1952:417-19) noted that _ferox_ burrows in deep water, and mentioned that in areas of bare white sand a group of fish invariably surrounds them, and one can locate buried softshells by observing these particular schools of fish. No mention was made of the turtles attempting to catch the fish. Other associations of soft-shelled turtles and fish have been described. Kirtland (_in_ DeKay, 1842:7) observed several large bass that closely followed large numbers of turtles floating at the surface. Newman (1906:131) reported the observations of fishermen in Lake Maxinkuckee that large-mouth black bass stay not far away from swimming softshells; the same author also mentioned the observations of Jacob Reighard, who suggested that bass may be feeding upon minnows that he noticed following softshells. Seemingly some sort of commensalistic relationship exists whereby fish acquire food that is dislodged by grubbing and scurrying of softshells. Probably food is pursued on occasion from a buried position, but this habit probably is not executed specifically for obtaining food. Newman (_op. cit._:129) was of the opinion that burrowing in shallow water is a habit to facilitate "warming up."

Marchand (_loc. cit._) also wrote of other notable underwater observations on _ferox_ in Florida. He commented on this turtle's inquisitiveness in deep water and unconcern upon being touched or even upon being handled to some degree. Calf-deep in soft mud, he noted a turtle that "emerged from the mud of the bottom, headed up toward shore, circled, and when about three feet above the bottom dived suddenly and completely disappeared." Marchand wrote that some areas on the bottom (Crystal Springs), which are rooted up by the burrowing of softshells, are bare and soft, and assume a characteristic, easily recognized, appearance.

Cahn (1937:180, 189) stated that the burrowing process consists of "flipping" the loose sand or silt over the back, whereas Conant (1951:159) described the process as a rapid lateral movement of the body. My observations of captives agree essentially with Conant's observations. The initial movement, directed at a slight angle, is principally with the forelegs although complemented by lateral movements of the body. When the turtle is approximately half buried, it makes rapid lateral movements of the body, which completely bury the turtle and orient its body in a horizontal position.

_Behavior and Adaptations_

Some characteristics of softshells that are often mentioned in the literature are: extreme shyness or wariness, ferociousness as captives, dazzling speed and agility on land and in water, and great dependence on aquatic environment. Certainly they are wary; and this wariness may account, in part, for the scarcity of observations of basking, and statements attesting to their great speed on land. To my mind, their reported ferociousness and savage disposition as captives is overrated; of the many softshells that I have collected, only a few attempted to bite. The extensibility of their long neck does warrant more careful handling than needs to be employed with other species. Holbrook (_in_ Hay, 1892:145) even wrote that they "will sometime leap up and give a loud hiss," and Newman (1906:130) wrote that "they hiss violently and thrust out the head." Wright and Funkhouser (1915:120) reported a captive _ferox_ that "could jump forward practically its own length." I have been bitten by individuals of _Kinosternon_, _Sternothaerus_, _Pseudemys_ and _Graptemys_, and cannot support the contention that softshells are more prone to bite than those species, a view shared by LeConte (_in_ DeKay, 1842:7); many softshells on initial capture will tend to withdraw the head completely for a short time. Newman (_loc. cit._) also wrote that recently captured specimens exude a thick, yellow, semi-fluid resembling yolk of an egg from the inguinal glands; the substance, however, is odorless but "undoubtedly homologous with the emission of the inguinal glands of the musk and snapping tortoises." Perhaps there is a difference in aggressiveness associated with geographic location, the age of the turtle or individual temperament.

Smith (1956:159), referring to _muticus_, wrote that they are the best swimmers of all fresh-water turtles, and perhaps of any turtles. Corresponding statements of other authors attesting to their speed and agility (including _spinifer_ and _ferox_) in water and on land are based principally on the published comments of Muller (1921:181), who observed that females disturbed while laying eggs "about fifty feet from water ... covered the distance faster than a man can run." Cahn (1937:180) also stated that _muticus_ on a "level, unobstructed sand beach ... can outrun a man," and (_op. cit._:181) can "capture fish with ease"; Cahn supported the latter statement by relating his observation of a _muticus_ that captured a small brook trout in a large tank. Smith (_op. cit._:162) wrote that _spinifer_ is "said to overtake bass." Doubtless they are good swimmers and they do scurry rapidly on land.

Published statements relating to the strictly aquatic existence of softshells especially _muticus_, are based on recognition of "its drastic adaptations to aquatic existence" (Carr, 1952:428); these adaptations presumably include pharyngeal respiration and the marked depression of body form. Pharyngeal respiration was demonstrated for _muticus_ and _spinifer_ (Gage, 1884; Gage and Gage, 1886), and was considered the principal type of aquatic respiration (some dermal and some cloacal) in _Trionyx spinifer asper_ by Dunson (1960). Cloacal bursae (anal respiration) are lacking in trionychids (Smith and James, 1955:88). Accessory pharyngeal respiration is meaningful in light of the information furnished by Agassiz (1857:282-83), who found that _Trionyx_ has a smaller lung capacity (weight of body in ounces/capacity of lungs in cubic inches = 16.9) than do some other genera (_Pseudemys_, 2.8; _Testudo_, 2.7; _Terrapene_, 1.1); corresponding values for more aquatic species were _Chelydra_, 9.3 and _Kinosternon_, 16.0. Cahn (1937:181), however, wrote that he has demonstrated pharyngeal respiration in individuals of _Pseudemys_, _Chrysemys_ and _Sternothaerus_, and Allen and Neill (1950:13) suggested that it occurs in _Macroclemys_. More conclusive data are required to detect a positive correlation between small lung capacity, pharyngeal respiration, and degree of restriction to an aquatic habitat.

The depressed, soft-margined carapace of softshells has been mentioned as an adaptation to facilitate burrowing in soft sand or mud, and more suited for concealment than for speed in aquatic locomotion (Carr, 1952:429; Smith, 1956:162). Nielsen (1951:264-65), commented that in various lotic invertebrates, dorsoventral flattening of the body was no commoner than in lentic invertebrates; he wrote that a dorsoventral flattening is a disadvantage to an animal in a strong current and is an adaptation "probably ... not to withstand the current directly, but to avoid it by seeking shelter in narrow crevices." Probably another aid to concealment, mentioned by Williams and McDowell (1952:272), is the plastral hinge.

Concealment of softshells is not enhanced by growths of algae on the carapace. Proctor (1958:637-38) reported that the common, epizoöphytic alga of chelonians, _Basicladia_, has never been reported from _Trionyx_; the same author recorded a large amount of filamentous algae, principally _Stigeoclonium_, but the algae could be easily wiped from the turtle, and Vinyard (1955:64) recorded an alga, _Dermatophyton radians_, attached to the skin of the legs of _Trionyx_. I noted a small patch of greenish scum growing near the insertion of the neck on a softshell (_spinifer_ from Lake Texoma); cursory examination by Dr. R. H. Thompson, disclosed one of the colonial ciliate protozoans (resembling _Opercularia_) with enmeshed green or blue-green algae. Evermann and Clark (1920:592) mention a _spinifer_ from Lake Maxinkuckee, Indiana, having a growth of _Opercularia_, covering the plastron.

_Movement_

The reported proclivity of softshells for a strictly aquatic existence has been over-emphasized; they are no more confined to aquatic habitats than some chelydrids (including kinosternids). In fact, there is a general parallel in habits between members of the two families, namely, a tendency toward a bottom-dwelling existence, and a burrowing habit. The alligator snapping turtle (_Macroclemys_) is probably the most aquatic fresh-water turtle in the United States. The common snapping turtle and some kinosternids are known to migrate overland. Kinosternids and trionychids bask frequently, and trionychids have been observed moving overland. Cox (1894:50) reported a _spinifer_ attempting to climb a narrowly-stepped, 12-foot dam on Mud Creek at Ravenna, Nebraska; the turtle failed after repeated struggles, once reaching a height four inches shy of the brim before tumbling back into the water. Duellman and Schwartz (1958:271) commented that adults of _ferox_ are often seen on roads bordering canals, and informants have told me verbally of similar observations. Conant (1930:61) reported an individual of _ferox_ that was "... walking across the main street in Venice [Sarasota County, Florida]." Softshells will travel overland in search for suitable nesting sites; Newman (1906:130) wrote that _spinifer_ will climb "steep railway embankments with considerable ease, in order to reach a sand pit some fifty yards from the water."

From an analysis of species-composition of large reservoirs and lakes and their adjacent smaller ponds in southern Illinois, Cagle (1942:162) concluded that softshells "travel overland far less often than do ..." other species, but that they are "probably the first to move as the water level falls." On the basis of further observations in the same region, Cagle (1944:15) wrote that softshells rarely move overland, and once trapped in a pool of water, they bury themselves and remain there. He related instances of several individuals having been dug from dried mud where the last remnants of a water pool had evaporated and he concluded that the home range is probably confined to one body of water. That fluctuations in water level affect the movement of softshells is suggested by Mr. William E. Brode's comment that a commercial fisherman trapped numerous softshells in the Pearl River, south of Monticello, Mississippi, in unbaited hoop-nets in late May and June when the water level was receding after heavy rains.

The meager data available concerning the aquatic movements of softshells indicate that individuals wander but little. Breckenridge (1955:6, table 1) found that among 30 recaptured turtles that had been marked, the greatest distance traveled was 600 yards over a two-year interval; after a three-month interval one originally captured 30 miles distant, moved only 200 yards. The statement of a professional turtle trapper mentioned by Breckenridge (_loc. cit._) and data previously presented (see page 436), to the effect that over-trapping results in increasingly diminished returns, tends to support the idea that there is little aquatic movement in soft-shelled turtles.