COSMAEIUM. 89 



C. CEUCiATUM, Breb. Plate XXI, figs. 23, 24. 



Length and breadth nearly the same, ends broadly trun- 

 cate; deeply constricted; sinus narrow, enlarged outwardly;^ 

 semi-cells trapezoidreniform, inferior angles obtuse; sides 

 incline towards the truncate end ; margins somewhat crenate. 

 Two nuclei in each semi-cell ; membrane finely granulate or 

 punctate. 



Diameter 22-24 ij. 



Swamp and marsh pools ; rather rare. 



C. Phaseolus, Breb. Plate XXI, figs. 28-32. 



Cells about as long as wide, smooth ; constriction deep, 

 forming a linear, excavated, notch on each side ; semi-cells 

 reniforni ; end view elliptic with a slight projection in the 

 middle of each side. 



A common species to be found, probably in every State of 

 the Union. 



0. BIEEME, Xord. Plate XXII, figs. 23, 24. 



Small, about as long as wide, deeply constricted, sinus 

 wide at the mouth ; semi-cells elliptic, base and back some- 

 what truncate ; in the center a large verruca ; viewed from 

 the end, elliptic, with a prominent cylindrical verruca in the 

 center of each side ; lateral view, obovate furnished with a 

 similar verruca. Membrane smooth. 

 Breadth 13 yu. ; length 14 yu. 



Denmark Pond and Biidd's Lake, N. .). 



0. SCHLIEPHACKEANUM, Gruu. Plate XXI. figs. 14, 15. 



Very small, subquadrate, as broad as long, smooth, entire, 

 deeply constricted; semi-cells depressed, ends broadly 

 truncate, or plane-convex ; sides convex, often projecting at 

 an obtuse angle ; center more or less inflated. 

 Breadth 12 )a. ; if not equal, slightly less in length. 



Occurs occasionally in large numbers, but more frequently 

 it is found singly in ponds of Pennsylvania, New Jersey, 

 :Massachusetts, Minnesota. 



J Cells with a central inflation, membrane granular. 



C. OENATUM, Ealfs. Plate XXI, figs. 39-45 ; Plate LX, figs. 



22-24. 



Cells of nearly equal length and breadth, constriction 



deep, narrow; semi-cells with a somewhat reniform base, 



angles broadly rounded, end truncate; sides inflated below, 



and contracted and concave near the end, thus producing a 



