SPECIES OF DESMIDS. 105 



s. Diameter ^-^ in. (31;*) or smaller (t). 



rfaf in. (60/1) or longer (). 



/. End straight, sides tapering into short, mostly obtuse processes, 



triconie, 126 



/. End convex; processes short, stout crenulatum, 126 



/. End concave; processes short, upwardly diverging, 



pusillnm, 130; Donnellii', 132 

 u. Processes short, robust, incurved; end of semi-cell truncate, 



cerastes, 133, 

 u. " long, narrow, incurved; end of semi-cell convex, 



ankyr aides, 1 3 7 



u. Processes long, horizontal tetracerum, 134 



v. Processes curved, apices bifid pentacladum, 129 



v. " " apices entire incisum, 132 



z/. Processes horizontally radiating; ends of cell with bifid papillae, 



pentacerum, 134 

 v. Processes horizontally radiating; ends without papillae, 



crenulatum, 126 



v. Processes upwardly diverging, the apices bifid . franconium, 13,1 

 w. Diameter -g-J-g- in. (40^) or smaller (x). 

 w - " sio- in - (7o/^) o r larger (7). 



x. Isthmus centrally ribbed; rays curved downward . comptum^ 129 

 x. not ribbed; in end view rays basally separated by an 



acute incision ' incisum, 132 



x. Isthmus not ribbed; in end view rays separated by a rounded 



sinus crenulatum, 126 



y. End with prominent papillae; diameter y-j-j- to y^^ in. (140-150^), 



Ophiura, 134 

 y. End with prominent papillae; diameter ^ f to ^ 7 in. (75-85^), 



coronulatum, 135, 

 y. End without prominent papillae; ray margins serrate, 



macrocerum, 134 

 y. " " ray margins granulate-crenate, 



hexacerum, 137 



s. End view oval, ends produced in a long, thin arm, ungulatum, 136 



2. fusiform fusiforme, 137 



5. End view triangular or 3-radiate (ad). 

 z. 4-radiate or angular (ee). 



z. " 5-radiate (ff) 



