TETMEMOBUB. 91 



T. Brebirsonii, (Mengh.) Ralfs. Plate XX, figs. 1-2; Plate 



L, fig. 36. 



Cells in front view cylindrical, not attenuated at the trun- 



cately rounded ends; in lateral view fusiform, attenuated from 



the middle to the rounded ends; cytioderm striately punctate. 



Cells four to six times longer than broad. 



Diameter 18-20 a. 



Frequent iu ponds everywhere. 



Yar. TUBGIDU8, Half-. Plate XX, figs. 1. 5. 



This variety i> larger, the constrictioD greater, and the semi- 

 cells Bomewhal inflated, it approaches in form T. granulatua 

 but is more constricted at the middle, it- puncta are arranged 

 in longitudinal lines, and, front and Bide views are unlike. 



Diameter K) 18 p.. 



T. ORANULATU8, Ralfs. Plate L, figs. 33, 34. 



Cells live to six times longer than broad, both in front and 

 lateral views, fusiform, and ending in a colorless projecting 

 lip- 1 ike process; slightly constricted in the middle. ( Ihlorophyl 

 osually with a longitudinal Beries of large granules. Mem- 

 brane irregularly punctate. 



Diameter 38-50 c 



Frequent in ponds, and readily recognized by its figure, 

 both in front and lateral views, fusiform. 



T. laevis, (Kg.) Ralfs. Plate L, fig. 36 ; Plate XX, fig. 3. 



In front view somewhat tapering with truncate ends; lateral 

 view fusiform ; punctae none or very indistinct ; four to sis 

 times longer than broad. 



Diameter 20-22 u. 



Not so frequent as the preceding, but not confined to any 

 particular localities. 



T. mintjtus, D. By. Plate XX, figs. 7, 8, 9. 



Smaller than the preceding, only three times longer than 

 broad, membrane smooth. 

 Diameter 18-20 u. 



Had this species from Florida, New Jersey aud Pennsyl- 

 vania. 



