Valve small, curved, with parallel dorsal and ventral margins; apices truncate and recurved into dorsal elevations; striæ delicate. Blue clay. Not common. Pl. 13, Fig. 32. {52}EUNOTIA PECTINALIS (KUETZ.) Valve linear, arcuate, apices slightly rostrate; striæ distinctly punctate with puncta in longitudinal rows nearer together at the ends. _Himantidium pectinale_ Kuetz. Common in fresh water. Pl. 13, Figs. 6 and 7. The fasciæ are associated in large masses, sometimes an inch or more in diameter, and late in August are found a foot or more in length, of a beautiful chocolate color. Exceedingly abundant in the cedar-swamp streams of the Pine Barren regions of New Jersey. In winter, the dead frustules form a parchment-like coating upon the twigs, dead leaves, and other débris on the borders of streams. This species can scarcely be referred to Dillwyn's Conferva pectinalis, as, in his description, quoting Mueller, he says that "the filaments are of a dirty green color; seldom exceeding half an inch in length." Dillwyn's form is probably Fragilaria virescens, which equals Fragilaria pectinalis Ehr., while Kuetzing's species is Fragilaria pectinalis Ralfs. It is not impossible to confuse Fragilaria virescens and Eunotia pectinalis when the zone only is seen under a low power and their mode of growth is similar. EUNOTIA PECTINALIS VAR. UNDULATA RALFS Valve as in type form, but with undulate margins. Common in the cedar swamps of New Jersey. Pl. 13, Figs. 8 and 10. EUNOTIA PECTINALIS VAR. SOLIEROLII (KUETZ.) Valve as in type, but with internal divisions as though in the process of reduplication. Not common. Moorestown, N. J. (Palmer). Pl. 13, Fig. 9. EUNOTIA PECTINALIS VAR. VENTRICOSA GRUN. As in type, but with the valves tumid in the middle. May's Landing, N. J. Pl. 13, Fig. 12. Fig. 11 is a form found in the blue clay. It differs in the coarser puncta from the var. ventricosa. In outline it resembles Eunotia arcus Wm. Sm., which is Ceratoneis arcus (Ehr.) Kuetz., but the central nodule is not present as in the latter form, which connects Eunotia and Cymbella. It may be a form of E. luna Ehr. (A. S., Atlas, Pl. 286, Figs. 33 and 34.) EUNOTIA VENERIS KUETZ. Valve with convex dorsal and straight ventral margins, more or less constricted near the sub-acute apices. Striæ subtle, punctate. _Eunotia incisa_ Greg. May's Landing, N. J. Blue clay, Pavonia, N. J. Pl. 13, Figs. 30 and 31. {53}EUNOTIA (PROPER) EUNOTIA LUNARIS (EHR.) GRUN. Frustules sessile, solitary or in clusters. Valve arcuate, narrow, attenuated toward the apices, which are sometimes slightly rostrate or rostrate-capitate; transverse striæ, 14 in 10 µ, punctate. Very common in ditches, especially in the spring. Variable in length. Pl. 12, Figs. 24 and 25. EUNOTIA HEMICYCLUS (EHR.) RALFS Valve semicircular, with obtuse apices; striæ transverse, punctate; terminal nodules minute and indistinct. Hammonton Pond, N. J. Rare. Pl. 12, Fig. 23.