t 



104 SPECIES OF DESMIDS. 



g. Angles in end view trifid .... .... trifidum, 123 



g. " " " simple or bifid {ss). 



h. Arras trifid or bifid; end view 3-4 radiate; arms smooth, 



brachiatum, 1 24 

 h. " " " end view 3-radiate; arms aculeate, rough, 



asptnosum, 143 

 h. " " •' end view 5-6 radiate distentum, 149 



h. " '' " end view 7-9 radiate .... Rotula, 135 



h. Arms truncate, oblique, geniculate, short; end view 4-radiate, 



inconspicu um, 125 

 h. Arms acute or aculeate, curved; end view3-radiate sudeticum* 



i. Ends separated by a more or less elongated isthmus (/). 

 /. Ends approximate (z). 



j. End view fusiform, with a central obtuse inflation, leptocladum, 136 

 j. " oval, a long arm on each side, 



grallato7-ium, 136; ungulatum, 136 

 /. End view triangular or 3-radiate [k). 

 J. " quadrangular or 4-radiate (/). 



J. " 5-radiate (»). 



/. " 6-radiate (w). 



j. " 7-8 radiate . , . ... Ophiura, 134 



k. Isthmus basally inflated; cuspidate or spinous (/). 



k. " not basally inflated; cuspidate not spinous {jii). 



I. Isthmus basally inflated . elongatum, 130 



/. " with a 1-4 cuspidate protuberance on each side; arms 



short fasciculoides, 130 



/. " with I notched spine on each side . . spinosum, 139 



m. Diameter -g-i-j- in. (50/^) or less (n). 

 '"• " roir '"• (6oy") or wider {0). 



n. End straightish, sides tapering into short, mostly obtuse processes, 



tricorne, 126 

 n. End broadly convex; processes curved .... cyrtocerum, 128 

 n. " " processes straight, slender . gracile, 133 



o. In end view the angles produced in long arms, 



vestitum, iT)^; pseudosebaldi, 139 

 o. In end view the angles not produced in long arms, Sebaldi, 138 

 p. Isthmus basally inflated or cuspidate (r). 

 p. Isthmus not basally inflated nor cuspidate {s). 

 r. Isthmus basally inflated, corrugated ■d.nAA&n^icvi\aXe,tetragonum, 130 

 r. " with a short spine on each side . . odontatum, 134 



*Journ. R. Micr. Soc, Dec, '85. 



