Valve linear, usually slightly gibbous in the middle and at the ends; raphe oblique; axial area less than one-third the width of valve, convergent at the ends; striæ, 7 or 8 in 10 µ, radiate in the middle, convergent at the ends, crossed by a narrow band. L. ? to 300 µ. Blue clay. Fresh water. Abundant at Middletown, Delaware Co. (T. C. Palmer). Pl. 28, Fig. 4. Fig. 9, Pl. 29, is one of a number of smaller forms which are difficult to determine, approaching P. viridis. PINNULARIA MAJOR VAR. PULCHELLA N. VAR. Valve strongly gibbous in the middle and gradually widened to the rounded ends; axial area broad, less than one-third the width of the valve, widened unilaterally in the middle; striæ, 7 in 10 µ, crossed by a band nearly as wide as the length of the costæ and scarcely distinct. L. 273 µ. {103}The central nodule is scarcely evident, probably because it is not so thick as in other forms. The outline is near to that of N. mesogongyla and certain forms of N. nobilis, differing from the latter in the median line, striæ and band which is wider than that of P. latevittata var. domingensis Cl. Hammonton Pond, N. J. Pl. 28, Fig. 2. A very beautiful form which I cannot find described or figured. It does not appear to be N. major var. turgidula Cl., which has a narrow band. In the fossil deposit from Hopkinton, N. H., valves occur similar in outline but smaller. PINNULARIA NOBILIS EHR. Valve slightly gibbous in the middle and at the ends; median line complex; striæ, 4 or 5 in 10 µ, slightly convergent or parallel at the ends, crossed by a band one-third as wide as the length of the striæ. L. ? to 350 µ. Blue clay. Fresh water. Pl. 28, Fig. 1. PINNULARIA DACTYLUS EHR. Valve broad, linear, slightly gibbous in the middle; ends broad, rounded; median line not complex, sinuous; striæ, 4 or 5 in 10 µ, crossed by a very broad band. L. ? to 300 µ. _Navicula gigas_ A. S. Blue clay. Fresh water. Pl. 28, Fig. 3. Forms occur which are with difficulty assigned to either nobilis or dactylus. PINNULARIA DACTYLUS VAR. DARIANA (A. S.) CL. Valve linear-lanceolate, obtuse; axial area broad, less than one-third the width of the valve; striæ, 6 in 10 µ, crossed by a broad band. L. 220 µ. Absecon, N. J. Pl. 29, Fig. 3. PINNULARIA DACTYLUS VAR. DEMERARÆ CL. Valve elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate, broad in the middle; median line flexuose; striæ radiate throughout, 6 in 10 µ. L. 150 µ. Blue clay. Pl. 29, Fig. 10. PINNULARIA GENTILIS (DONK.) CL. Valve linear, with rounded ends; axial area about one-fourth the diameter of the valve; striæ radiate in the middle, convergent at the ends, 7 in 10 µ, crossed by a broad indistinct band. Fresh water. Not common. Pl. 29, Fig. 1. PINNULARIA TRIGONOCEPHALA CL. Valve linear, gibbous in the middle and at the cuneate ends; axial area wider between the middle and the ends, dilated to an elliptical space in the middle; striæ, 6 in 10 µ. L. 145 µ. Blue clay.