STAURASTRUM. 1 63 



stricted, sinus acute, widening rapidly outwards ; semi- 

 cells subelliptical or fusiform, lower margin ventricose, 

 dorsal margin strongly convex ; lateral angles gradually 

 produced to form short, stout, strongly incurved processes, 

 tipped with about 3 spines and with 2 or 3 series of den- 

 ticulations beneath ; apex with a dorsal series of spines, 

 often deeply bifid, stretching from angle to angle, and 

 frequently with a lateral series just beneath as well. 

 Vertical view 3-5-radiate, angles produced into short 

 tapering processes all bent abruptly in one direction ; 

 lateral margins concave with a marginal row of spines, 

 often displaced by the twisting of the processes. 



Zygospore roughly globose, somewhat angular, with 

 numerous short, much branched spines. 



Length 25-65 u. ; breadth, including processes, 33-75 [i; 

 breadth of isthmus 7-1 2 ^ ; diam. zygosp., without 

 appendages, 27-37 ^ ; including appendages, 50-80 (JL. 



ENGLAND. Cumberland ! Westmoreland ! (Ralfs). 

 Lancashire ! W., N., and E. Yorks ! Leicester (Roy). 

 Burnham Beeches, Bucks ! Gloucester (Ralfs). Surrey ! 

 Sussex (Ralfs). Hants ! Dartmoor, Devon (Harris). 

 Cornwall ! 



WALES. --Llyn Padarn !, Snowdon !, Capel Curig ! 

 (Cooke & Wills), Llyn-y-cwm-ffynon !, Llyn Gwynant ! 

 and Bettws-y-coed (Roy), Carnarvonshire. Dolgelly, 

 Merioneth (Ralfs). 



SCOTLAND. General (Roy & Biss.). 



IRELAND. --Donegal ! Clare Isle, Mayo ! Kerry ! Dublin 

 and Wicklow (Arch.). 



Geogr. Distribution.- -France. Germany. Galicia and 

 Austria. Italy. Norway. Sweden. Denmark. Finland. 

 L^nited States. 



St. controversum is closely allied to St. aculeatum, from which 

 it differs in its relatively smaller size and its more strongly 

 developed and incurved processes, which are usually bent, 

 giving the specimens a very distorted appearance. It is a very 

 variable species, and the lateral series of spines is not always 

 present, but the dorsal row is usually very strongly developed. 



