BRITISH DESMIDIE^. 139 



******** Frond spinous or rough with spine-like granules which are 

 incrassated, emarginate, or divided*. 



t Spines minute, inconspicuous and granule-like . 



30. S. cyrtocerimi (Breb. ); frond rough with minute granules; seg- 

 ments in the front view somewhat triangular with short incurved 

 processes. 



Euastrum , Bailey, American Jonrn. of Science and Arts, v. 41, t. 1. 



f. 6 (1841). 

 Staurastram cyrtocerum, Brebisson, in lit. cion icone (1846). 



Dolgelley and Penzance, /. R. Near Bristol, Mr. Broome. Piltdown 

 Common and near Pulborough, Sussex, Mr. Jenner. 



United States, Baileij. Falaise, Brebisson. 



Frond rather larger than that of Staurastrum tricorne, deeply constricted 

 at the middle, rough with minute spine-like granules, which on the processes 

 are arranged m transverse lines. The segments are truncate and taper towards 

 their junction, so that the constriction forms a broad notch on each side. The 

 spines on the outer margin are larger than those on the rest of the segment, 

 and frequently are obscurely notched. The end view has three blunt angles, 

 much like those of Staurastnwt tricorne, and usually a little curved. 



The sporangia are orbicular and their spines slightly forked at the apex. 



Staurastrum cyrtocerum is smaller than S. aculeatiim and S. controversum, 

 and its spines are far less conspicuous. It is best distinguished by its con- 

 verging processes. 



Length of frond -^^ of an inch ; breadth -j^ ; breadth at constriction 



1 • 



2747 • 



Tab. XXII. fig. 10. a. front view; 6. end view. 



31. S. asperum (Breb.) ; segments elliptic or somewhat cuneiform, 

 rough with minute spines, which on the outer margin are usually- 

 dilated at the end or forked. 



a. Angles in end view rounded. 



/3. proboscidewn, Br^b. ; angles in end view prolonged into short 



rays terminated by minute spines. 



Staurastrum asperum, Brebisson, in lit. cum icone (1846). 



Penzance, J. R. Yate near Bristol, Mr. Broome and Mr. Thwaites. Near 

 Pulborough, Sussex, Mr. Jenner. 



Falaise, Brebisson. 



Frond comparatively large, rough with minute acute granules or spines ; 

 segments slightly tapering on the inner side, so that their figure is somewhat 

 cuueate, and the constriction forms a wide notch on each side. The outer 



* Staurastrum polymorphum has occasionally a few scattered spines, but 

 they are simple. 



