98 DESMIDS OF THE UNITED STATES. 



series of granules ; lateral view subrectaugular oblong ; end 

 view elliptic with central inflation. 

 Diameter 50 /*. ; length 56-58 jn. 



Sluggish waters, Northampton Co., Pa. 



Genm, TETMEMORUS, Balls. 



Cells cylindrical or fusiform, slightly constricted in the middle, 

 narrowly incised at each end, but otherwise entire. Cytioderm 

 mostly punctate or granulate. 



The cells are elongated as in Penium, from which, however, 

 this genus may be distinguished by the incised ends and by the 

 central constriction. 



T. BREBISSONII, (Menegh.), Ralfs. Plate XXIII, figs. 1-2; Plate 



LXI, 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 ^. 



Frequent in ponds everywhere. 



Var. TURGLDUS, Ealfs. Plate XXIII, figs. 4, 5. 



This variety is larger, the constriction greater, and the 

 semi-cells somewhat inflated. It approaches in form T. 

 granulatus, but is more constricted at the middle, its puuctae 

 are arranged in longitudinal lines, and front and side views 

 are unlike. 



Diameter 40-48 /*. 



T. GKANULATUS, Ralfs. Plate LXI, figs. 33, 34. 



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

 lateral views, fusiform, and ending in colorless projecting 

 lip-like process ; slightly constricted in the middle. Chloro- 

 phyl usually with a longitudinal series of large granules. 

 Membrane irregularly punctate. 



Diameter 38-50 yu. 



Frequent in ponds, and readily recognized by its figure, 

 both in front and lateral views, fusiform. 



T. LAEVIS, (Kg.), Ralfs. Plate LXI, fig. 35; Plate XXIII, fig. 3. 



In front view somewhat tapering with truncate ends ; 

 lateral view fusiform ; punctae none, or very indistinct :, 

 four to six times longer than broad. 



Diameter 20-22 //. 



