COSMARIfM. 87 



one-half the diameter of the cell ; end view usually a regular 

 ellipse ; lateral view of cell oblong with central constriction. 

 Diameter 20-24 fx. 



Frequent In ponds. Reinsch describes several forms ; a 

 larger and a smaller size, one with straight ends, another 

 emarginate ; end view usually elliptic. Among our varieties 

 I find one with inflated center ; of eleven drawings made in 

 my sketch book nine are without central inflations, and two 

 with them, the latter even more inflated than the variety 

 retusiforme, found in Norway, and described by Wille. 



C Nymanniantjm, Grun. 



Cells somewhat hexagonal, finely punctate ; semi-cells 

 slightly broader than long ; base rather flat, sides converging 

 from the base to the broadly truncate end, lower part promi- 

 nently rounded, sinuate near the end ; apex often refuse. 

 Diameter 36-38 yu. ; length 50 pi. , more or less. 



In front view, this is a common form, barely separable from 

 the following — C sublobatum ; in lateral, and in end view 

 however, they ought to be distinct by the absence or the 

 presence of a central inflation. All the specimens examined 

 personally evidenced more or less of an inflation, or at least 

 a tendency to it; have not been convinced of having a genu- 

 ine C. Nymannianum.- I set them down to C. sublobatum. 

 Semi-cells with central inflation; cytioderni smooth or punc- 

 tate. 



C. TuEPiNii, Breb. Plate XX, figs. 24, 25. 



Cells of equal length and breadth ; constriction deep, forms 

 a narrow linear or acute-angled sinus, outwardly ampliated ; 

 semi-cells triangular, lower angles rounded, apex truncately 

 rounded; sides somewhat concave; central inflation granu- 

 late, and sometimes emarginate ; cytioderm finely granulate 

 or punctate. 

 Diameter 55-VO //. 



Not rare ; frequently in large numbers in ponds. New Jer- 

 sey, Pennsylvania and other States. 



C. SUBLOBATUM, Archcr. Plate XXI, figs. 21, 22. 



Cells somewhat oblong, aboiTt one -half longer than broad, 

 sinus linear ; semi cells swollen at the base, gradually nar- 

 rowed toward the truncate ends; inferior and superior angles 

 rounded ; apex broadly truncate, sides sinuate ; with central 

 inflation. 



Diameter 38-44 ix. 



Ponds, Pennsylvania, New Jersey ; not abundant, but 

 probably widely distributed. 



