STAURASTRUM. 91 



The specimens figured on PL CXLI, f. 18, from Ireland are 

 not exactly typical, being more or less intermediate in form 

 between St. Icevispinum and the next described species, St. sub- 

 lcevispinum. The processes are less attenuated and not so 

 divergent as in typical St. Icevispinum and the " body " of the 

 cell is not quite as large. They have more in common with 

 St. Icevispinum, however, than with St. sublcevispinum. 



108. Staurastrum sublsevispinum W. & G. S. West. 



(PL CXLI, fig. 19.) 



St.subhedspinutii West & G. S. West, Desm. U. S. 1898, p. 314, t. 18, f. 20-22; 

 Alg. Ceylon, 1902, p. 179; Further Corrtrib. Plankt. Scott, Lochs, 1905, 

 p. 502, t. 7, f. 23. 



Cells small, 1| times broader than long (including the 

 processes), deeply constricted, sinus open and obtuse ; 

 semicells with a very small : body," angles produced 

 into finger-like strongly diverging processes, with parallel 

 sides and conical apices ; apex of semicell concave. 

 Vertical view triangular, body : small, and processes 

 stout. Cell- wall smooth. 



Zygospore unknown. 



Length 25-33 ^ ; breadth 37-46 JJL ; breadth of isth- 

 mus 7-8'o [JL. 



SCOTLAND.- -Plankton of Loch Fadaghoda, Lewis, 

 Outer Hebrides ! 



Geogr. Distribution. Ceylon. United States. 



St. sublcevispinum is closely related to St. Icevispinum, from 

 which it is distinguished by its relatively greater breadth, and 

 smaller " body of the semicell ; its processes are cylindrical 

 and only abruptly attenuated at the apex. 



109. Staurastrum subnudibrachiatum W. & G. S. 



West. 



(PL CXLI, fig. 20.) 



St. subnuii;bi',<<-hi,-ttni,i West & G. S. West, Further Contrib. Freshw. Phyto- 

 plankton Scott, Lochs, 1905, p. 502, t. 7, f. 18, 19. 



Cells of medium size, about H times broader than 

 long, including the processes, body of cell slightly con- 



