The genus Pseudo-Eunotia was created by Grunow for forms like Eunotia, but without terminal nodules. As, however, in E. lunaris and E. hemicyclus nodules are evident, although not so large as in many species, I include these two forms as heretofore under Eunotia. EUNOTIA BICEPS EHR. Valve linear, slightly arcuate, narrow, with rounded apices somewhat revolute; striæ, 16 in 10 µ. May's Landing, N. J. Pl. 13, Fig. 27. EUNOTIA PRÆRUPTA EHR. Valve convex on dorsal side, apices dilated and truncate; striæ distant at centre. Common in the blue clay. Pl. 13, Fig. 5. EUNOTIA PRÆRUPTA VAR. BIDENS GRUN. Valve with two undulations; otherwise as in type. _Eunotia bigibba_ Greg. With the type. Pl. 13, Fig. 19. EUNOTIA ROBUSTA RALFS Valve arcuate, with several or numerous dorsal ridges or crenæ which decrease in relative size in proportion to their number. Striæ radiate, variable in distance apart, and in size of puncta. Ralfs included under this one name the following species named by Ehrenberg: E. diodon (2 crenæ); E. triodon (3); E. tetraodon (4); E. pentodon (5); E. diadema (6); E. heptodon (7); E. octodon (8); E. enneadon (9); E. decadon (10); E. hendecadon (11); E. duodecadon (12); E. serra (13); E. prioritis (14); all more than 20, E. polyodon. E. scalaris, with from 15 to 17 crenæ, and E. icosodon with 20, may be added. It is probable that all of these forms occur at May's Landing, N. J. The forms with more than eight crenæ are comparatively rare. In the blue clay those with from four to six are most common. Pl. 13, Figs. 13, 14, 15, 16, 17, 21, 24, 25. {54}EUNOTIA BACTRIANA EHR. Valve linear, apices revolute, acute, dentate on the dorsal margin, with one acute crena near each end. Tom's River, N. J. Rare. Pl. 13, Fig. 18. EUNOTIA BIDENTULA WM. SM. Valve with straight ventral margin, and with two undulations on the dorsum; apices large, rounded. May's Landing, N. J. Rare. Pl. 13, Fig. 20 (not Schumann's form, which has angular crenæ). EUNOTIA FORMICA EHR. VAR.? Valve turgid in the middle and at the apices which are unilaterally truncate. Pensauken, N. J. (artesian well). Pl. 13, Fig. 26 (not a typical form). The following are forms which appear to be indeterminate, or, in any case, are scarcely worthy of distinction by specific names, as might be said of others of the innumerable variations of this genus: Fig. 23, Pl. 13, probably a form of prærupta. Newtown Square. Fig. 28, Pl. 13, from the blue clay. Fig. 29, Pl. 13, an asymmetrical form, apparently abnormal, but not rare at May's Landing, N. J. Fig. 17, Pl. 38. Valve convex on the dorsal side, incised on the ventral; striæ about 15 in 10 µ, closer at the ends; L. 30 µ. Schuylkill River. Fig. 18, Pl. 38. Valve arcuate, asymmetrical, broader at one end; terminal nodules large; striæ, 10 in 10 µ; L. 47 µ. Gloucester, N. J., artesian well. Numerous variations of the above species are illustrated in Schmidt (Atlas, Pls. 285-291). ACTINELLA LEWIS (1865)