44 BRITISH DESMIDIACE.E. 



JJ Semicells elliptical or subpyrainidate-truncate, cells 

 as long as broad, or only a little longer than 

 broad, widest part of the semicell at the base or 

 middle region, never at the apex. 



83. St. yladiosum. 



84. St. teliferuni. 



85. St. Hystrix. 



86. St. Brebissonti. 



87. St. pilosum. 



88. St. hirsutuin. 



89. St. muricatum. 



90. St. pyramidatum*. 



91. St. Ravenelii. 



tjj Semicells narrowly subelliptic, broadest at the apex, 

 which is distinctly flattened. 



92. St. erasiun. 



93. St. erostdlum. 



70. Staurastrum pungens Breb. 

 (PL CXXXV, figs. 8-10.) 



Xtaurasimm y)ungens Breb. in Ralfs, Brit. Desm. 1848, p. 130, t. 34, f. 10 ; 

 Arch, in Pritch. Inf. 1861, p. 738 ; Pxabenh. Krypt.-fi. Sachs. 1863, p. 193 : 

 Flor. Europ. Alg. 1868, p. 214 ; Lund. Desm. Suec. 1871, p. 64 (forma) ; 

 Cooke, Brit. Desm. 1887, p. 144, t, 50, f. 6; Hansg. Prodr. Algentt. 

 Bohm. 1888, p. 214 : De Toni, Syll. Alg. 1889, p. 1148": Heimerl, Desm. 

 Alp. 1891, p. 606; Borge, Siissw. Chlor. Archang. 1894, p. 38; Roj^ & 

 Biss. Scott. Desm. 1894, p. 24 ; Comere, Desm. de France, 1901, p. 167, 

 t, 12, f. 24 ; West & G. S. West, Alg. N. Ireland, 1902, p. 45, t. 2, f. 29 ; 

 Brit, FreshAv. Phytoplankton, 1909, p. 203. 



Cells small, about as long as broad, or a little longer, 

 deeply constricted ; sinus acute, opening widely ; semi- 

 cells broadly subfusiform or somewhat cuneate, dorsal 

 margin slightly convex, ventral margin very tumid, 

 angles subacute and ending in a strong spine ; apex of 

 semicell also provided typically with two accessory 

 spines between each pair of angles, projecting obliquely 

 upwards, but one or other of these may sometimes be 

 reduced or wanting. Vertical view triangular, sides 

 straight or only very slightly concave, angles broadly 

 rounded, tipped with a stout spine, and with two equally 

 strong spines projecting from each lateral margin. Cell- 

 wall minutely punctulate, punctulations arranged in 

 concentric circles round the angles. 



Zygospore unknown. 



