76 DBSMIDS OF THE UNITED STATES. 



C. dentatum, Wolle. Plate XIII, fig. 15. 



Cell about one-half* longer than wide; constriction deep, 

 forms gaping sinuses ; cytioderm rather closely set with small 

 pearly granules; the margins of the rounded sides of the 

 semieells dentate with large and distant conical projections, 

 or teeth ; ten to twelve on each side. The end- broadly 

 rounded are devoid of projecting teeth. End view of cell 

 oval; lateral view elliptic with a constrictioo in the middle. 

 Diameter 90-100 /'.: length 145-160 n. 



This plant has hitherto been found only in Pennsylvania, 

 New Jersey, Florida and Massachusetts. 



It is separated from C. <>ru/> , its nearest kin, by the shape 

 of the semieells, which are not triangular, or conical, hut 

 broadly oval, and by the nudity of the apices. 



('. latum, Breb. Plate XI 11, Bg. 1 1. 



Large, slightly longer than broad : constriction deep, 

 sinuses narrow, somewhal enlarged within; semieells broad 

 reniform, side- rounded, and back (dorsum ) broad, rather flatly 

 rounded, margins dentate-crenulate ; cytioderm covered with 

 pearly granules which are disposed in curved, concentric 

 series. 



1 hameter about 60 ". 



Bears a resemblance to C. margartiiferum, but it is some- 

 whal Larger ; and according to Brebisson, more flatly rounded 

 in the middle, and base more reniform. Find it rather rarely 

 intermingled with other forms, and >oinetimes miestion the 

 characters for a good species. 



C. RENIPORME, (Ralfs). Arch. Plate XIV. figs. 10, 11. 



A diagnosis of this species would not differ from the last, 

 C. latum, except iii the size of pearly grannie-, which are 

 nearly twice as large, (well shown in the empty cell fig. 11) 

 and in the more decided reniform figure of the semieells. 



The only habitat hitherto found for this form, is a pond in 

 Florida ; collected by J. Donnell Smith of Baltimore, 

 Md., 1879. 



( '. OCHTHODE8, Xord. Plate XIV, figs. ''>. I. 



( Jells one and one-half times longer than broad, somewhat 

 elliptic-oblong, deeply constricted, sinuses narrow linear ; semi- 

 cells semicircular or subtriangular, sides convex : apices trim- 



