SPECIES OF DESMIDS. 107 



jj. Surface granules emarginate or divided; semi-cells broadly elliptical, 



asperum, 127 

 JJ. " not emarginate; semi-cells elliptic, truncata, 128 



jj. " not emarginate; semi-cells subsemiorbicular, 



angles truncate . . . muricatum, 127 



jj. Surface scabrous, semi-cells elliptic . .... scabrum, 130 



jj. Surface tuberculate; sides at base convex, spinous; a central, 



spherical, spinous projection conspicuous . . . bullosum.* 

 jj. Surface tuberculate; sides at base concave; no central protuber- 

 ance . .... tuberculatum.* 

 jj. " " " " not concawt, pseudocrenatum.** 



kk. End view sides concave (//). 



kk. " sides nearly straight, very slightly convex (nii). 



kk. " sides convex; semi-cells subsemiorbicular, 



muricatum, 127 



//. Semi-cells twisted; 2-3 times longer than wide, elliptic or oblong, 



alternans, 128 

 //. Semi-cells not twisted (7m?i). 

 mm. Front view ends concave; end view angles rounded, 



striolatum, 126 

 mm. " " end view anglesacute, Pringlei, 132 



mm. Front view ends convex; end view angles crenate, sides smooth, 



crenatum, 126 



mm. " " end view angles not crenate, somewhat 



truncate . . ... . dilatatum, 128 



mm. " " end view angles granulate, rounded, 



erasum.** 

 nn. Diameter j-jVo 'i^- (^5/^) O"" '^^^ • • pygmcBum, 128 



nil. " greater than y^Vsr ''^- (^Sy"); end broadly truncate, 

 sides slightly convex or nearly straight, converging, 



botrophilum, 131 

 nn. Diameter greater than y^iVir i"^- (^S/^); end rounded, sides convex; 

 semi-cell elliptic . . rugulosum, 127; punctulatum, 127 



00. End view 3-radiate or angular, sides nearly straight (//). 

 00. " " " sides concave (;-r). 



00. End view 4-radiate or angular {xx). 



pp. Cells spinulose on the whole surface aculeatum. 140 



pp. " on the margins only setigerum, 141 



*Journ. R. Micr. Soc, Feb. 1886. 

 **F.-w. Algee, p. 42 et seq. 



