74 DE6MIDS OF THE UNITED STATES. 



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 centre a circular cluster of larger granules. 

 Diameter 25-30 u.. 



Frequent in pond at Elmira, X. Y., 1882. 



\ Membrane granular without a central inflation. 



C. MABGARITIFERUMj Menegh. Plate XIII, figs. 1-3. 



('ells about one one-half times longer than broad, sinus 

 narrow, usually more or less enlarged outwardly; setnieell 

 semiorbicular, somewhat reniform or oval, with rounded in- 

 ferior angle-, convex sides and broadly rounded, not truncate 

 end. Cytioderm rough with pearly granules; end view 

 elliptic; zygospore- orbicular. 

 Diameter 25-50 fl. 



This species varies in size and form. The rough memhrane 

 distinguishes it from C. crenatum and C. undulatum; its 

 rounded ends from C. Botrytu, it- -mailer size and less positive 

 kidney form from C. reniforme. It appears to he as widely 

 distributed as the most common of this genus. 



' . i'Uncti i.a 1 1 \t, Breb. I Mate XIII. fig. 1. 



This form i- very similar to < '. margaritiferwrn, but it is 

 smaller, the pearly granules less conspicuous, and the ends 

 more flattened. The membrane is sometimes not granular, but 

 punctate. It i- found in the same localities, and appears very 



nearly related. 



Diameter of eells 20-30//. 



C. BOTRYTIS, Menegh. Plate XIII, tig-. 5-7. 



('ells one, and nearly two times as long as broad; sinus 

 narrow linear; semicells with nearly straight base, sometimes 

 inclining to reniform ; sides converging from the inferior 

 rounded angle- to the flat, truncate end ; cytioderm evenly 

 covered with large pearly granules. Zygospores orbicular. 

 spinous with long, thin spines, the end- much divided. 

 Diameter 35-62 //. 



A very common plant, and very variable in the size, and 

 in the proportions of length and breadth. 



