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. SECTION 1. HIMANTIDIUM EUNOTIA MAJOR (WM. SM.) RAB. Valve arcuate, linear, subcapitate, recurved. Striæ punctate, 12 in 10 µ L. 90-190 µ. Common in fresh water. Pl. 13, Figs. 1 and 2. EUNOTIA GRACILIS (EHR.) RAB. Valve with sides parallel; apices slightly capitate and revolute; striæ, 10 in 10 µ. The striæ on the connective membrane more delicate than in E. major. Intermediate forms occur. Common in fresh water. Pl. 13, Fig. 3. Fig. 4 is indeterminate. EUNOTIA NYMANNIANA GRUN.