66 DESMIDS OF THE UNITED STATI 



in triangular form on basal part. Isthmus fully half of the 

 diameter of the cell. 

 Diameter 57-63 /i. ; length 60-68 /i. 

 Ponds, Minnesota. 



C. BIOCULATUM, Breb. Plate XVIII, figs. 21, 22. 



Cells small, somewhat longer than broad ; constriction 

 deep, producing a gaping notch on each side. Semi-cell 

 compressed, oval, with convex base, short convex sides and 

 rather flat apex. Cytioderm smooth or finely punctate. 

 Zygospore globose, without spines. 

 Diameter 15-16 //. ; length about 17 yw. 



Rhode Island, Massachusetts, Pennsylvania, New Jersey, etc. 



C. RHOMBUSOIDES, Wolle. Plate XLIX, figs. 6, 7. 



Cells nearly as long as wide ; semi-cells in form of a rhom- 

 bus, sides all equal, straight or slightly convex ; nearly half 

 as long as broad; sinus between, deep and wide; isthmus 

 one- fourth of diameter; end view rhombus like; membrane 

 finely punctate. 



Diameter 55-65 yu. ; length 50 /*. 



From collections made by Mrs. Hanson and Miss Haggin 

 in pools near Lake Tahoe, California, August, 1886. 



C. LOBATULUM, Wolle. Plate XLVIII, figs. 33, 34. 



Small, one-third longer than broad, end of semi-cell 

 broadly truncate ; sides convex with a slight contraction 

 near the apex ; side view circular with end truncate. Mem- 

 brane finely and closely punctate, or granular. 

 Diameter 25 yw. ; length 33 p. 

 Ponds, Minnesota. 



C. QUIMBYII, Wood. 



Cells small, subelliptical, profoundly constricted in the 

 middle, joined by translucent bauds into families ; semi-cells 

 seen from the front elliptical, and nearly twice as long as 

 broad ; from the vertex elliptical, from the side roundish. 

 Chlorophyl masses single in each cell. Cytioderm thin, 

 smooth. 



Diameter 18 p. ; length 25 /A 



"This plant was found in a spring near Camden, N. J. r 

 upon whose bottom it formed a gelatinous translucent, green- 

 ish mass. The cells are joined by bands into families, in 

 which the little parent cell is generally very distinct, it, or 



