SPECIES OF DESMIDS. I09 



V}'. Diameter -j^ in. (38/1) or less [zz). 

 yy. Diameter greater than (38yu) -^^ incli {A), 

 zz. Cytioderm aculeated, aculei larger and denser at the angles, 



teliferum, 140 

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

 zz. " spinous; margins dentate . convexum.* 



zz. " " margins crenate , Ravenellii, 143 



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



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



Brebissonjiii, 141 

 A. " " aculei evenly covering the surface, 



Saxonuutn, 141; hirsutum, 141 

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



A. " " spines or short processes notched, 



spongiosu7n, 148 



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

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

 B. '' " " processes both on and within the margins i^F'). 

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



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

 nences . xiphidiophorinn .** 

 B. " " " •' " " each with 2 promi- 

 nences . . simplex.** 

 B. End view 4-aagled, 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, 



eustephanum, 147 



C. " lateral margins smooth . . . pseudofurcigerum, 147 



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

 smooth . ... cunealum, 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. 



Kite helm, 150 

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



Tohopekaligense.** 



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

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



