80 DESMIDS OF THE UNITED STATES. 



rounded angles, three within the margins, and three near 

 margin between the angles (sometimes the grannies appear 

 to border the whole semi -cell); on the margin of the sides 

 near the inferior angles two larger grannies, and within the 

 margins a few scattered smaller ones ; end view quadran- 

 gular-oval, with two series, usually of six larger granules, 

 on each of the longer sides, one of the series on the margin, 

 and the other within. Zygospores spherical, with long 

 spines, fig. 6. 



Diameter of cell 40 yu. ; length about 50 //. 

 Ponds, Pennsylvania and New Jersey. 



The nearest approach to this species is C. Un(i< rimmm, 

 Naeg. It is separated by its smaller size, the details of out- 

 line and the arrangement of the larger granules. 



C. NORDSTEDTII, Delp. Plate XL VIII, figs. 23-25. 



Cells somewhat longer than broad, constriction deep ; 

 semi-cell rectangular oblong about twice as wide as long, 

 granulate around the margins, center usually nude. 



I adopt this name for a form widely distributed, but va- 

 riable ; sometimes it resembles C. triplicatum in size and 

 shape, but differs in the number and arrangement of the 

 granules, which are not in series of threes, but in continuous 

 eccentric rows. Sometimes they cover the upper half of the 

 semi-cell, then again only one or two rows occur within, but 

 close to the margin ; the center and basal half are usually 

 nude. The sides are not so straight as figured by Delpoute, 

 but the front and end views are always more or less rec- 

 tangular-oblong. 



Beinsch has named a very different form C. Nordstedtii; it 

 is nearly, if not entirely, identical with C. cyclicum, Lund. 



C. SEELYANUM, Wolle. Plate XXI, figs. 33-35. 



Cells small, quadrangular, deeply constricted ; sinus nar- 

 row linear ; semi-cells twice as wide as long, with a small 

 rounded notch in the middle of the sides, the superior angles 

 somewhat produced laterally; dorsum slightly produced in 

 the middle and crenated ; membrane at the superior, and at 

 the inferior angles and near the margin of the ends, each 

 with three or four granules ; in the center a circular cluster 

 of larger granules. 

 Diameter 25-30 yu. 



Frequent in pond at JEhnira, N. Y.,1882. 



Membrane granular without a central inflation. 



