266 BEscRTPTio?! OF \_Poli/ffastriea. 



STAtrRASTRiJM poli/moiyhum. — lloTigli, with minute granules, having 

 on each side a short process tipped yrith spines ; end view thix-e to 

 six rayed. Much smaller than S. gracile, deeply constricted ; seg- 

 ments irregular in form, but generally broader than long. Spo- 

 rangia orbicular; their spines few and forked, (P. 13, figs. 20, 21, 

 24, 25, 31.) 



The segments are very variable in form, and often resemble those 

 of S. tricorne, and S. margaritaceiim, but in these species the processes 

 are never spinous. S. polymorphum is smaller and less spinous than 

 S. asperum. Length 1-lOOOth. 



S. gracile. — Rough, elongated on each side into a slender process, 

 tenninated by minute spines ; end view, triradiate. Frond deeply 

 constricted at the middle ; granules in transverse lines on the pro- 

 cesses. It differs from S. tricorne in its elongated processes termi- 

 nated by minute points. Length 1 -773rd to 1 -539th. 



S. Arachne. — Minute, rough, with minute granules, suborbicular, 

 with elongated, slender, incurved processes ; end view with five 

 linear rays. Eemarkable by its slender processes. Very rare. 

 Length l-1026th. 



S. tatracerum = S. paradoxum (Ehr.) — Minute, rough; front view 

 with four slender diverging processes, entire at the apex ; end view 

 compressed, with a process at each extremity. Length 1 -2703rd. 

 (P. 2. f. 102, 103.) 



S. paradoxum. — Veiy minute, rough ; front view with elongated 

 diverging processes, which are minutely trifid at the apex ; end view 

 quadi'angular, or sometimes triangular. 

 Var. (5.) — End view triradiate. 



Frond generally much constricted ; ends tnmcate ; each segment 

 has generally, four elongated processes diverging from those of the 

 other segment. S. tetraceriim has but two processes to each segment, 

 and these are also undivided, and more slender than those of S. para- 

 do.mmi. Length 1-94 1th. 



(H.) Frond spinous or rough, with spine -lilce granules, which are 

 incrassated, ema/rginate or divided, 



f Spines minute, inconspicuous, and granule-like. 

 S. cyrtocerum. — Rough, with minute granules ; segments in front 

 view somewhat triangular, with short incurved (converging) pro- 



