SPECIES OF DESMIUS. 109 



yy. Diameter -^ in. (38^) or less (ss). 

 yy. Diameter greater than (38/1) -^ inch (A). 

 ' 22. Cytioderm aculeajted, aculei larger and denser at the angles, 



telifcrum, 140 

 zz. Cytioderm aculeated except at the centre, echinatum, \^\\pecten y 141 



zz. spinous; margins dentate convex-urn* 



zz. " margins crenate .... Ravenellii, 143 



A. Cytioderm aculeated, aculei geminate .... sociatum, 142 

 A. " " aculei not geminate, densest at the angles, 



Brebissonnii, 141 

 A. " aculei evenly covering the surface, 



Saxonicum, 141; hirsutum, 141 

 A. Cytioderm spinous, spines not notched . . . echinatum, 141 



A. spines or short processes notched, 



spongiosum, 148 



B. End view 3-angled; processes within the margin, 6 in number (C). 

 B. " " " " " " 3 in number (D). 

 B. " processes both on and within the margins (jp). 

 B. " " processes at the angles only (). 



B. End view 3-angled, angles broadly truncate, each with 3 promi- 

 nences . . . xiphidiophorum** 



B. " "' " " " " each with 2 promi- 

 nences simplex** 



B. End view 4-angled, body quadrangular, ends of arms trifid, 



Osceolense** 



B. End view 3 or 4-lobed, emarginate or bifid; cell very irregular or 



quadrate enorme, 151 



C. Front view lateral margins crenate; basal margins crenate, 



eu step ha n um, 147 

 C. lateral margins smooth . . . pseudofurcigerum, 147 



C. " lateral margins with 3-6 sharp teeth; basal margin 

 smooth cuneatum, 148 



D. Cytioderm granular furcigerum, 146 



D. Cytioderm smooth; end view angles produced into 2 processes, a 



third above and between them Pottsii, 151 



D. Cytioderm smooth or finely punctate; end view angles notched, 



Kitchellii, 150 

 . Processes 9, nearly as long as semi-cell diameter, ends furcate, 



Tohopekaligense. * * 



*Jour. R. Micr. vSoc., Feb., 1886. 

 **F. W. Algee, p. 41 et seq. 



