Chapter III: Preface (3)

In Diatoma and Fragilaria, we find a punctum or pore at one end of a valve, but not in line with the pseudoraphe; in Synedra, a minute pore is usually found in the position of the terminal nodule and, in some species, indications of a central nodule are observed; the median line is wider but there is no raphe. In the fresh-water Synedræ, many of which are among the longest of diatoms, living in running streams, the terminal nodules are much more indistinct, while the marine forms have distinct terminal nodules, are not, as a rule, found in bands, and assume a more naviculoid outline.

SYNEDRA VAUCHERIÆ VAR. PARVULA (KUETZ.) RAB.

Valve lanceolate, with produced or rostrate apices; pseudo-nodule wide, excentric. L. 17 µ.

Crum Creek.

Pl. 12, Fig. 5.

Fig. 6 represents a variety with coarser striæ from the Schuylkill River. Both are easily mistaken for Fragilaria intermedia.

{50}SYNEDRA FULGENS (GREV.) WM. SM.

Frustules geminate or flabellate on a stipe. Valve slightly inflated in the middle and at the apices; pseudoraphe narrow; striæ finely punctate, radiate at the ends.

Marine. Atlantic City.

Pl. 11, Fig. 10.

SYNEDRA AFFINIS KUETZ.

Valve lanceolate; striæ marginal, leaving a broad lanceolate pseudoraphe.

Common along the coast.

Pl. 12, Fig. 3.

SYNEDRA AFFINIS VAR. PARVA (KUETZ.) V. H.

Valve lanceolate, slender; striæ marginal, shorter than in the type.

_Synedra gracilis_ Kuetz.

Common along the coast.

Pl. 12, Fig. 7.

SYNEDRA AFFINIS VAR. TABULATA (AG.) V. H.

Valve linear-lanceolate; striæ, 11 in 10 µ, very short.

Not common. New Rochelle.

Pl. 12, Fig. 4.

ASTERIONELLA HASSALL (1855)

(dim. of aster, a star)

Frustules linear, slightly inflated at the ends, arranged in star-shaped clusters which soon break up. Valve linear, unequally inflated at the ends.

ASTERIONELLA FORMOSA HASS.

Valve clavate at the ends; striæ transverse, 17 in 10 µ, pseudoraphe very narrow or indistinct; an ovoid, hyaline area at each end.

Newark, N. J. Broomall's Lake, Media (Palmer).

Pl. 12, Figs. 19, 20, 21.

ASTERIONELLA INFLATA HEIB.

Valve linear, capitate at each end and tumid in the middle; striæ distinctly punctate; pseudoraphe indistinct, or not apparent. L. 30 µ.

Fresh water. May's Landing, N. J.

Pl. 12, Fig. 22.

EUNOTIINÆ

_Eunotia._--Frustules either free, in fasciæ or epiphytic. Valves arcuate.

_Actinella._--Frustules, solitary or in small clusters, cuneate. Valve inflated at one end.

{51}EUNOTIA EHR. (1837) em. GRUN. (1862)

(eu, well, and noton, a back, referring to the strong, ridged dorsum)

Frustules free, in fasciæ or epiphytic. Valve arcuate, without costæ, transversely striated; pseudoraphe absent; pseudo-nodules at each end.

Chromatophores laminate along the concave zone and the valves.

Very many species of Eunotia have been created to differentiate size and number of crenæ or undulations. An examination of certain fossil deposits of New England, as well as a gathering from the blue clay of Philadelphia, will show forms which vary infinitely. E. major and E. gracilis are scarcely distinguishable because of the intermediate variations. The striæ in all forms are punctate, but the puncta are frequently confluent.

ANALYSIS OF SPECIES

Eunotia is divided into two sections, Himantidium and Eunotia proper. In Himantidium, the frustules are in fasciæ, either short or long. Among those with short fasciæ are major, gracilis, and nymanniana; those with long fasciæ are pectinalis, solierolii and veneris. Eunotia proper includes frustules, free or epiphytic, in which the valves are not dentate on the dorsal margin, such as lunaris, hemicyclus, biceps and prærupta; and those in which the valves are dentate or crenate on the dorsum, such as monodon, triodon, diadema and others.

The resemblance between Eunotia and Epithemia is noticeable. In both, the epiphytic character of the valve is seen in the shape of the frustule which is arched, and, in the free forms, is adherent at the ends only. In Epithemia, the median is more evident than the terminal nodules. In Eunotia, there is no median nodule, but the end nodules, in some species, are quite evident, and a tendency is shown to produce a very short raphe. The arrangement of puncta in valve view is similar in both genera.