90 SPECIES OF DESMIDS. 



s. Ends rounded; semi-cells subsemicircular, with 8-10 crenulations, 



Sendtnen'anuM* 

 J. Ends truncate; semi-cells pyramidal; cells small, . . notabik, 66 

 J-. " sides almost parallel; diameter -^^ to -g-^-j- in. 



(30-38/^), crenatum, 67 



J-. " sides converging; diameter ys^s" ^"^^ (^o/^), 



Nagelianum, 67 

 /. Semi-cell quadrate, smooth, angles rounded; end retuse or convex, 



quadraium, 59 

 t. " pyramidal or subquadrate; end undulate, Holmiense, 68 



t. " " end truncate; diameter -,^ to -g-J-j-in. (32-36yu), 



integrum, 68 

 A " " " diameter ytjVo' ^o tsW '"■ (2°-24/<), 



Hammer i, 79 

 /. " " end rounded, surface smooth, octogonum.* 



t. Semi-cell pyramidal, punctate, base flat, angles rounded, 



ansatum, 68; Nymannianum, 79 

 t. Semi-cell sub-semicircular, end truncate, sides with 2 emargina- 



tions; smooth .... Braunii* 



u. Ends truncate. Diameter -g^ to Y^-g^ in. (2o-30yu), punculatum, 74 

 u. Ends convex. Diameter -j-jW '^^ tsW ^'^ (i4~i6/i) . . Iceve, 62 

 z/. Cell twice as long as wide, rectangular; sinus linear, not widened, 



sinuosum, 65 

 v. Cell less than twice as long as wide; semi-cell pyramidal, 



Venus turn, 68 

 V. " '• " " semi-cell subquadrate, small, 



Meneghinii, 65 

 w. Sinus narrow, not widened outwardly; cell elliptical, end convex, 



variolatum 63; exiguum, 66 

 ■w. Sinus widened and rounded inwardly, narrowing outwardly, cell 



wider than long obsoletum, 64 



-w. Sinus widened outwardly; semi-cell oval, base and end convex, 



contractum, 63 

 w. " " " " base and end flattend, 



depressum, 64 

 w. Sinus widened outwardly; semi-cell quadrate, Meneghinii, 65 



w. " " semi-cell subsemicircular, end rounded; 



diameter -j-^-j- to -g\^ in. (75-ioo/<) . . pachydermum, 70 



X. Margins crenate or granulate (jc). 

 X. Margins not crenate nor granulate {bU). 



* F.- — -w. Alga;, p. 27 et seq 



