Pl. 16, Fig. 29. C. pediculus and C. placentula are the only species I have found in fresh water. Cleve states that the former occurs also in brackish water. The following are among the species placed by Cleve in a new genus, Eucocconeis, distinguished by the absence of a loculiferous rim. COCCONEIS DIRUPTA GREG. Valves elliptical, the lower with fine puncta in slightly radiating lines, a narrow axial area and a central area dilated into a lanceolate, stauriform space; the terminal fissures turned in opposite directions; the upper valve similar to the lower valve except in the absence of raphe and nodules. Along the coast. New Rochelle. Pl. 16, Fig. 22 (lower valve). COCCONEIS PELLUCIDA GRUN. Valves elliptical, the upper with broad axial area on each side of which are fine, longitudinal rows of short striæ; the lower valve with more numerous longitudinal rows, a marginal line and indistinct raphe; the terminal fissures small and turned in opposite directions. New Rochelle. Pl. 16, Figs. 25 and 26. In the var. minor Grun. the median line of the lower valve is sometimes slightly sigmoid. ACHNANTHES BORY (1822) (achne, froth or down, and anthos, a flower) Frustules stipitate, solitary or in short fasciæ, flexed. Valves elliptical or lanceolate, naviculoid, dissimilar, the lower with a raphe and median and terminal nodules, and the upper with a pseudoraphe or median space. The genus has no apparent affinity with any other. ACHNANTHES LONGIPES AG. Valves linear-elliptical, obtuse at the apex, sometimes slightly constricted in the middle. Connective zone with transverse, subtly punctate striæ, interrupted by longitudinal lines. Central nodule of lower valve dilated into a stauros reaching the margin. Valves costate, the costæ alternating with double rows of fine puncta. Along the coast, in estuaries. Pl. 16, Figs. 1 and 2. A. longipes is the only species in our locality considered by Cleve as belonging to the genus; the other forms, distinguished by the absence of costæ, are included in the genus Achnanthidium of Kuetzing. In A. longipes, the chromatophores consist of scattered, rounded granules, while in Achnanthidium the chromatophore is a single plate along the upper valve, or a double one {59}along the connective zone. It is necessary, therefore, to distinguish between A. longipes and the following group, but, because of the long continued union of all of the stipitate forms having the general appearance of a true Achnanthes, I shall continue to describe the local species under the generally accepted name. ACHNANTHES BREVIPES AG. Valves without costæ; striæ moniliform; upper valve with excentric pseudoraphe or median line; otherwise as in A. longipes. Along the coast, in estuaries. Pl. 16, Fig. 3. ACHNANTHES SUBSESSILIS KUETZ. Valves linear-elliptical, rounded at the ends; upper valve with excentric pseudoraphe; striæ moniliform, puncta smaller than in A. brevipes. Along the coast, in estuaries.