EUNOTIINÆ
Eunotia.—Frustules either free, in fasciæ or epiphytic. Valves arcuate.
Actinella.—Frustules, solitary or in small clusters, cuneate. Valve inflated at one end.
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.