88 DESMIDS OF THE UNITED STATES. 



C. EETUsrii, Perty. Plate XXI, figs. 25, 26. 



Small, of nearly equal length and breadth, entire ; sinus 

 deep, linear; semi-cells with subreniform base, sides sinuate 

 and converging to a truncate end; angles rounded; end 

 view centrally protruding. 

 Diameter 22-30 yu. 



Pennsylvania and Xew Jersey. 



C. JIAEGAEITLTJI, Wolle. Plate XXII. figs. 25. 26, 27. 



Suborbicular, from one to one and one-third times as long 

 as wide; sinus narrow linear; semi-cells somewhat semi- 

 circular, margins undulate crenate. or emarginate ; two or 

 three surface swellings near the base which cause prismatic 

 reflections from the smooth pearl-like membrane. 

 Diameter 22-25 //. 



Found the first of this form in Splitrock pond, Xew JereeVf 

 but occasioaally since in other localities of the same State, 

 and in Pennsylvania. 



C. TiTHOPHOHU.M, Xord. Plate XXII. figs. 2S. 29, 30. 



Cells about as long as wide, circular, deeply constricted ; 

 sinus an acute angle considerably ampliated (angle about 

 20°); semi-cells from the base cuneate-semicircular ; end 

 view elliptical with a prominent central elevation ; laterally 

 seen, obovate-eircular with a mamilliform prominence on 

 each side. 



Diameter 28 ja. ; length 80 /^. 



Collected this form from ponds on Mount Everett, Mass. It 

 corresponds so nearly with a plant found on the island of 

 Java, described by Dr. Xordstedt, I adopt the name as his- 

 choice. 



C. HOMALODEEMU3I. Xord. Plate XX, figs. 19, 20. 



Slightly longer than broad, deeply constricted ; sinus 

 narrow linear with the mouth considerably ampliated ; semi- 

 cells trapezoid with a subreniform base ; sides refuse : ends 

 truncate, and often refuse ; superior angles obtuse, inferior 

 broadly rounded ; seen from the vertex, elliptic-oblong with 

 the middle somew^hat inflated; lateral view ovate. Ends 

 about half as wide as the breadth of the cell. Cytioderm 

 finely, often indistinctly, punctate. 

 Diameter 40 n. 



Ponds, Mount Everett, ilass. 



The typical plant was found in the Arctic region, on the 

 island of Spitzbergen. It is described by Dr. Xordstedt as 

 measuring 48-51 u. in diameter, about one-flfth larger than 

 ovir plant ; hitherto found only in one locality, IJsl and 1882. 



