28 FRESH-WATER ALG^ OF THE UNITED STATES. 



C. LOBATULUM, Wolle. Plate LVII, 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 /* ; length 33 yw. 

 Ponds, Minnesota. 



C. CIRCULATE, Eeinsch. Plate LVII, fig. 37. 



Cells nearly circular 5 present form slightly shorter than 

 broad ; sinuses narrow linear ; lateral view ovoid, end view 

 elliptic ; isthmus one-third of diameter of cell ; membrane 

 finely punctate. 



Diameter 75-85 yw ; length 70-75 yw. 



Frequent in Marsh pools, Tocoi, Florida. This form is 

 considerably larger than the one described by Keinsch, and 

 not quite equal in length and breadth, but otherwise very 

 near it and certainly nearer than the plant described by 

 Lundell under the same name. 



C. PERFORATUM, Lund. Plate LVII, fig. 32. 



Somewhat circular, slightly longer than broad, moderately 

 constricted in the middle, sinus acute angled, enlarging out- 

 wardly, rarely linear ; semi-cells sub-semi-circular, back 

 high convex with the middle slightly flattened or rarely 

 slightly retuse ; end view broadly elliptical ; lateral view 

 circular with base broadly truncate. Membrane distinctly 

 but sparsely punctate often with larger granules arranged 

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

 diameter of the cell. 



Diameter 57-63 ja ; length 60-68 jw. 

 Ponds, Minnesota. 



* 



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



Cell 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 ^ length 50 /*. 



From collections made by Mrs. Hanson and Miss Haggin 

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



