Frustules cuneate, narrow, usually found in twos. Valve clavate, hyaline, rather broad at the base; septa moderately deep; pseudoraphe indistinct; striæ, 27 at the base, 30 in the middle and 33 at the apex in 10 µ. _Gomphonema tinctum_ Ag. Along the coast. Abundant from about the middle of July to the middle of August. Pl. 9, Figs. 14 and 15. LICMOPHORA BAILEYI (EDW.) GRUN. Frustule broadly cuneate or with convex margins, rarely almost orbicular; valve spatulate or ovate with slender, produced base; septa very deep; pseudoraphe distinct; striæ 20 in 10 µ. _Podosphenia baileyi_ (Edw.) Lewis. Long Island Sound and upper coast of New Jersey. This form is placed in a doubtful position by Mereschkowsky. As it corresponds more closely to the Paradoxæ, it is placed here provisionally. The girdle face and apex of the valve are round, the pseudoraphe is distinct and the septa deep, but the stipe is short. Pl. 9, Fig. 10 and Pl. 38, Figs. 3 and 4. LICMOPHORA LYNGBYEI (KUETZ.) GRUN. Frustule cuneate, slightly rounded at the angles. Valve oblanceolate; pseudoraphe distinct; septa deep; striæ, 12 in 10 µ below, and 16 in 10 µ above. _Podosphenia lyngbyei_ Kuetz. Along the coast. Pl. 9, Figs. 3 and 4. LICMOPHORA EHRENBERGII (KUETZ.) GRUN. Frustule cuneate, broad. Valve obovate-lanceolate; pseudoraphe wide; striæ coarse, 8 in 10 µ, moniliform. _Podosphenia ehrenbergii_ Kuetz. Along the coast. Pl. 9, Fig. 5. MERIDION AG. (1824) (merizo, I divide) Frustules in zone view cuneate, adnate in circular or spiral fasciæ, at length becoming free. Valve symmetrical with respect to the longitudinal axis, more or less cuneate; costæ and striæ transverse. Chromatophores numerous, small, elongated, in irregular rows on the zone (Pfitzer). MERIDION CIRCULARE (GREV.) AG. Transverse costæ coarse, variable in number and distance apart, sometimes interrupted or indistinct; striæ interstitial, 16 in 10 µ. In springs and small streams of pure water. _Echinella circularis_ Grev. {41}Meridion constrictum Ralfs, sometimes given as a variety of M. circulare, differs only in the constriction below the apex. The two kinds of frustules are usually found growing together and as the variation is often extremely slight they are here included under the earlier name. Pl. 10, Figs. 1, 2 and 3. Fig. 1 represents the constricted form which is the more common. Fig. 3 is a sporangial form.