DESMIDS OF THE UNITED STATES. 72a 



C. Braunii, forma major, Eeinsch. Plate XLYITI, figs. 28, 29. 



Cells small, one and one-half times longer than broad, sinus 



narrow linear ; sides with two emarginations ; ends truncate, 



membrane smooth ; lateral view oval ; vertical view elliptic. 



Diameter 25-28 yu. ; length 36-40 yu. 



Ponds, Stillwater, Minnesota. 



C. (JEuastrum,) Sendtnerianum, Eeinsch. Plate XL VIII, figs. 

 30, 31. 

 Cells nearly twice as long as wide ; sinus narrow linear ; 

 semi-cells nearly as long as wide, ends rounded, lateral 

 margins each with four or five crenulations ; lateral view of 

 whole cell elliptic with more or less of a constriction in the 

 middle ; end view oval. 



Diameter 25 /'. ; length 44 ^. 



C. NiTiDULTJM, De Not. Plate XXI, figs. 16, 17, 18 ; and Plate 

 LXIII, figs. 9, 10. 

 Cells small, smooth, of nearly equal length and breadth ; 

 constriction deep, sinuses narrow linear; basal angles of 

 semi-cells obtusely rounded, sides rounded, ends roundly 

 truncate; viewed from the vertex elliptic; from the side, 

 subovate. 

 Diameter 22-30 ju. ; length 25-35 /^. 



Not infrequent in pond waters. The figs. 16, 17, should 

 have the ends moderately 'flattened. 



C. PSEUDONiTiDULUM, ISTord. Plate XXI, fig. 19. 



Varies from the preceding in its somewhat larger size and 

 more quadrangular form. The basal angles of the semi-cells 

 besides being rounded, protrude slightly. 

 Diameter 38 //. 



Pound this form only in Northampton County, Pennsyl- 

 vania. 



C. LAEVE, Eab. Plate XVIII, fig.^lO. Var. Septbntrionale, 

 Wille. Plate XLIII, fig. 14. 

 Cells one and one-third to one and two-thirds longer than 

 broad, constriction deep; sinus narrow linear; semi-cells 

 with high-rounded ends, usually somewhat retuse. Cytio- 

 derm finely granular. 

 Diameter 14-16 /a. 



