Io8 SPECIES OF DES-MIDS. 



rr. Cells spinulose, a short, irregular process on each side, 



controversum, 143 

 rr. Cells spinulose on the margins of the long, colorless, diverging 



arms ... aspinosum, 143 



ss End view triangular or 3-radiate (iiii). 

 ss. " 4 or 5-angular or radiate (//). 



ss. End view circular, with usually 9 short, marginal, notched pro- 

 cesses Eloiseanum, 149 



tt. End view margins smooth; spines short; semi-cells in front view 



twice as wide as long avicula, 123 



tt. End view margins smooth; spines short; semi-cells in front view 3 



or 4 times as wide as long . .... commutatum, 124 



tt. End view margins smooth; spines on the angles only, very long, 



longispinum, 145 

 tt. " spines on the margins and surface as well as on 



the angles Mmnesotense.**" 



tt. End view margins verrucose, the verrucse emarginate or not, 



forficulatum, 144 

 //. " " denate, angles usually 3 . monticulosuvi, 144 



uu. End view margins smooth, concave; angles notched, 



quadr angular e, 145, 

 uu. " " crenate; spines long, divergent. 



Nova Cmsarece, 145; 

 uu. " " spinous; angles produced, furcate, 



forficulatnm, 144. 

 vv. End view triangular; aculei short, Hystrix, 142; trideniiferum, 142 

 vv. " " spines long, colorless, 



tricornutum, 145; Iriquetrum.**' 

 vv. End view 4-angled, angles broadly rounded, spines scattered; 



sides concave Hystrix, 142 



vv. End view 5 -angled, sides concave . . . Brasiliense, 146 



WW. Angles with numerous setae as long as the lobes; cells in front 

 view cruciform .... . cruciatum, 142 



WW. Angles with 4 teeth, 2 projecting upward, 2 downward, 



Cerberus, i^t 

 WW. ■' 2 spines; margins concave, spinous 



quaternium, 144 

 XX. Sides unequally produced, spinulose or spinous, controversum, 143 

 XX. Sides equally produced, spineless; angles spinous aculeatum, 140 



**F.-w Alg:e, p. 41 et seq. 



