Chapter XIV: Section I: MONOCYRTIDA, Haeckel, 1862, Monogr. d. Radiol., pp. 280, 281 (3)

_Cyrtocalpis obliqua_, var. _ovulum_, Haeckel, 1862, Monogr. d. Radiol.,
p. 286, Taf. v. fig. 3.

Shell smooth, broad, ovate, with very numerous and small regular circular pores, quincuncially disposed, twice as broad as the bars. Mouth without peristome, about half as broad as the shell.

_Dimensions._--Shell 0.09 long, 0.047 broad; mouth 0.04 broad.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

9. _Cyrtocalpis obliqua_, Haeckel.

_Cyrtocalpis obliqua_, Haeckel, 1862, Monogr. d. Radiol., p. 286, Taf. v.
figs. 4-11.

Shell smooth, irregularly ovate, more or less oblique, variable in size and form, sometimes nearly spherical, at other times subcylindrical. Pores subregular, circular, once or twice the breadth of the bars. Mouth simple without peristome, about half as broad as the shell.

_Dimensions._--Shell 0.07 to 0.1 long, 0.05 to 0.08 broad; mouth 0.03 to 0.04 broad.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

{1188}10. _Cyrtocalpis gromia_, n. sp. (Pl. 51, fig. 11).

Shell rough, ovate, very thick-walled, with subregular, circular pores of somewhat variable size. The diameter of the internal, simple, subspherical cavity is five to six times as great as the thickness of the wall. Mouth tubular, cylindrical, very narrow, only one-sixth as broad as the shell.

_Dimensions._--Shell 0.16 long, 0.11 broad; mouth 0.02 broad.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 530. _Mitrocalpis_,[147] Haeckel, 1881, Prodromus, p. 427.

_Definition._--#Archicorida# with a double ovate or ellipsoidal shell, composed of two parallel lattice-plates, which are connected by numerous beams. Apex without horn.

The genus _Mitrocalpis_ and the following closely allied _Spongocyrtis_ differ from the four preceding genera of Archicorida in the complicated structure of the shell-wall, which in the former is double, in the latter spongy. The mouth is in both genera constricted, narrow, and the apex without a horn. _Mitrocalpis_ has been derived probably from _Cyrtocalpis_ in the same way as _Peripyramis_ from _Bathropyramis_, by development of spines on the surface of the shell, which at equal distances from the latter become connected by branches, thus forming an outer envelope.

1. _Mitrocalpis palliata_, n. sp.

Shell ellipsoidal, large, one and a third times as long as broad. Inner shell very thin-walled, with irregular, polygonal pores of very variable size and form. From its nodal points there arise numerous bristle-shaped radial beams, about as long as the diameter of the mouth, which are connected at equal distances from the surface by delicate threads, forming the outer enveloping shell. The surface of the latter is smooth. The thin bars of the inner shell are twice to four times as broad as those of the outer. Mouth about one-seventh as broad as the shell, with a short tubular peristome.

_Dimensions._--Shell 0.35 long, 0.27 broad; mouth 0.04, distance of both shells 0.037.

_Habitat._--Central Pacific, Station 271, surface.

Genus 531. _Spongocyrtis_,[148] Dunikowski.

_Spongocyrtis_, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien,
vol. xlv. p. 31.

_Definition._--#Archicorida# with a spongy ovate shell, the wall of which is composed of irregular spongy wickerwork. Apex without horn.

The genus _Spongocyrtis_ differs from most other Monocyrtida in the spongy structure of the shell, which is found in only very few other genera of #Cyrtoidea#, e.g., in _Spongopyramis_ and _Spongomelissa_. It has been derived either from the similar {1189}_Cyrtocalpis_ by development of irregular spongy wickerwork on the surface of the simple lattice-shell; or from _Arachnocalpis_ (Pl. 98, fig. 13) by loss of the peristome.

1. _Spongocyrtis montis ovis_, Dunikowski.

_Spongocyrtis montis ovis_, Dunikowski, 1882, Denkschr. d. k. Akad. d.
Wiss. Wien, vol. xlv. p. 31, Taf. vi. figs. 67, 68.

Shell broad, ovate, rough, spongy, thick-walled; length to the breadth = 4 : 3. Spongy framework very dense and dark, with very small roundish pores. Mouth constricted, with a short tubular peristome, about one-third as broad as the shell.

_Dimensions._--Shell 0.35 long, 0.26 broad; mouth 0.08 broad.

_Habitat._--Fossil in the Alpine Lias (Schafberg bei Salzburg, Dunikowski).

2. _Spongocyrtis arachnoides_, n. sp.

Shell ellipsoidal, spiny, spongy, thin-walled; length to the breadth = 3 : 2. Spongy framework loose and delicate, with irregular polygonal meshes and arachnoidal thread-like bars. Mouth constricted, without peristome, about one-fifth as broad as the shell. (Very similar to _Arachnocalpis ellipsoides_, Pl. 98, fig. 13, but without corona around the mouth.)

_Dimensions._--Shell 0.32 long, 0.21 broad; mouth 0.04 broad.

_Habitat._--Central Pacific, Station 270, depth 2925 fathoms.

Subfamily 2. ARCHICAPSIDA, Haeckel, 1881, Prodromus, p. 428.

_Definition._--#Cyrtocalpida#, with the basal mouth of the shell fenestrated (vel Monocyrtida eradiata clausa).

Genus 532. _Halicapsa_,[149] Haeckel, 1881 Prodromus, p. 429.

_Definition._--#Archicapsida# with an apical horn.

The genus _Halicapsa_, and the following closely allied _Archicapsa_, represent together the small subfamily of Archicapsida, or of those Cyrtocalpida, in which the basal mouth of the simple shell is closed by a lattice plate. This may be the original state of this family, if it is derived from the Circospyrida (_Circospyris_, _Dictyospyris_) by loss of the sagittal constriction and the primary ring. But it is also possible that the Archicapsida have been partly derived from the Archicorida by secondary fenestration of the open mouth. The genus _Halicapsa_ may be easily confounded with the similar Ellipsid _Lithapium_ (compare p. 303, Pl. 14, figs. 8-10). The skeleton of both genera may be perfectly similar, the only distinction being the structure of the central capsule, which in _Halicapsa_ is that of the MONOPYLEA, in _Lithapium_ that of the PERIPYLEA.

{1190}Subgenus 1. _Calpocapsa_, Haeckel.

_Definition._--Surface of the shell smooth or rough, but not spiny.

1. _Halicapsa lithapium_, n. sp. (Pl. 97, fig. 6).

Shell pear-shaped, rough, one and a half times as long as broad. Pores subregular, circular, twice as broad as the bars. Basal plate with four larger ovate cortinar pores (two larger cardinal and two smaller jugular), and with six smaller peripheral pores (fig. 6). Horn of the apex three-sided pyramidal, stout, half as long as the shell.

_Dimensions._--Shell 0.16 long, 0.1 broad; horn 0.08 long.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

2. _Halicapsa triglochin_, n. sp. (Pl. 53, figs. 3, 4).

Shell ovate, rough, a little longer than broad. Pores regular, circular, hexagonally framed, of the same breadth as the bars. Basal plate (fig. 4) without larger pores. Horn pyramidal, stout, about half as long as the shell, with three short, horizontally divergent secondary spines at the base (possibly remnants of three original cortinar feet?)

_Dimensions._--Shell 0.11 long, 0.09 broad; horn 0.06 long.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

3. _Halicapsa prunoides_, n. sp.

Shell pear-shaped, tuberculate, a little longer than broad. Pores irregular, roundish, of different sizes. Basal plate with four larger and six smaller pores. Horn pyramidal, stout, about one-third as long as the shell. (May belong perhaps to the similar #Prunoidea# _Lithapium_, compare p. 303 and Pl. 14, figs. 8-10.)

_Dimensions._--Shell 0.14 long, 0.12 broad; horn 0.05 long.

_Habitat._--Fossil in Barbados.

Subgenus 2. _Echinocapsa_, Haeckel, 1881, Prodromus, p. 429.

_Definition._--Surface of the shell spiny, covered with thorns, papillæ or larger spines.

4. _Halicapsa papillata_, n. sp.

Shell bottle-shaped, papillate, one and a half times as long as broad. Pores circular, much larger in the middle part than towards the poles. The elevated frames between them bear on the {1191}nodal points large blunt conical papillæ. Basal plate without larger pores. Horn three-sided pyramidal, one-third as long as the shell, gradually passing into the slender neck of the bottle.

_Dimensions._--Shell 0.22 long, 0.15 broad; horn 0.07 long.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

5. _Halicapsa pyriformis_, Haeckel.

? _Haliomma pyriforme_, Bailey, 1856, Amer. Journ. Sci. and Arts, vol
xxii. p. 1, pl. i. fig. 29.

Shell pear-shaped, a little longer than broad, covered with numerous short conical spines. Pores subregular, circular, of nearly equal size, twice as broad as the bars. Basal plate with four crossed larger ovate pores (two larger cardinal and two smaller jugular pores). Horn stout pyramidal, scarcely one-fourth as long as the shell.

_Dimensions._--Shell 0.16 long, 0.14 broad; horn 0.04 long.

_Habitat._--Fossil in Barbados, living in the North Pacific (Kamtschatka)?

6. _Halicapsa hystrix_, n. sp. (Pl. 53, figs. 5, 6).

Shell pear-shaped, subspherical, a little longer than broad, with scattered stout pyramidal spines about as long as the radius of the shell. Pores subregular, circular, three times as broad as the bars. Basal plate (fig. 6) without larger pores. Horn very large, pyramidal, longer than the shell.

_Dimensions._--Shell 0.1 long, 0.09 broad; horn 0.13 long.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

Genus 533. _Archicapsa_,[150] Haeckel, 1881, Prodromus, p. 428.

_Definition._--#Archicapsida# without apical horn.

The genus _Archicapsa_ differs from the preceding _Halicapsa_ in the absence of the apical horn, and represents the simplest form among the Monocyrtida clausa, a simple, ovate, or pear-shaped shell without any appendages. The characteristic structure of the basal lattice-plate (with three or four large cortinar pores) makes it probable that _Archicapsa_ has been derived either from _Halicapsa_, by loss of the horn, or directly from _Dictyospyris_, by reduction of the sagittal ring and constriction.

1. _Archicapsa triforis_, n. sp. (Pl. 53, figs. 1, 2).

Shell pear-shaped, smooth, one and a half times as long as broad. Pores subregular, circular, of about the same breadth as the bars. Basal plate (fig. 2) with three very large pores, three times as broad as the others (one odd sternal pore and two paired cardinal pores).

_Dimensions._--Shell 0.09 long, 0.06 broad.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

{1192}2. _Archicapsa quadriforis_, n. sp.

Shell ovate, rough, a little longer than broad. Pores subregular, circular, twice as broad as the bars. Basal plate with four larger ovate cortinar pores (two smaller jugular and two larger cardinal pores).

_Dimensions._--Shell 0.12 to 0.15 long, 0.1 to 0.12 broad.

_Habitat._--Central Pacific, Station 265 to 268, depth 2700 to 2900 fathoms.

3. _Archicapsa nonaforis_, n. sp.

Shell pear-shaped, thorny, one and a half times as long as broad. Pores regular, circular, small, hexagonally framed, twice as broad as the bars. Basal plate with nine cortinar pores (three larger alternating with three pairs of smaller pores, as in Pl. 87, fig. 2).

_Dimensions._--Shell 0.14 long, 0.09 broad.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

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