1GO BRITISH DESMIDIACE^E. 



A variety with long and slightly diverging processes, 

 and the arrangement of the verrucse very similar to that 

 of St. anatinum. 



Length, without processes. 35 p ; breadth, including 

 processes. 86-1 02 p ; breadth of isthmus 13'5fju 



IRELAND. --Near Glenties, Donegal! Arderry Lough, 

 Galway ! 



In the front view this variety bears a striking resemblance to 

 St. anatinum, but in the end view it has the characteristic bifur- 

 cate spines of St. vestitum: 



Var. semivestitum West. (PL CLII, figs. 7, 8.) 



St. vestitum var. semicestitnm West, Alg. Engl. Lake Distr. 1892, p. 20, f. 38 ; 

 West & G. 8. West, Alg. 8. England, 1897, p. 496. 



Cells smaller than in the type : apex of semicell nearly 

 straight ; in vertical view triangular, processes bent 

 round all in one direction as in St. cyrtocemm, with one 

 furcate spine at the base of the convex side of each 

 process. 



Length, including spines, 20-28 \L ; breadth, including 

 processes, 34-42*5 (JL ; breadth of isthmus 4-8 \L. 



ENGLAND.- -Loughrigg and Brandreth, Westmoreland ! 

 Puttenham Common, Surrey ! Gunwen Moor, Corn- 

 wall ! 



In this small variety the spines are very much reduced. The 

 whole of the dorsal series is usually absent, and frequently the 

 whole of the lateral series as well, with the exception of one 

 bifurcate spine on the lateral margin. Some forms closely 

 resemble St. controversum, but the processes are longer and quite 

 straight. 



152. Staurastrum aculeatum (Ehrenb.) Menegh. 



(PL CLIII, figs. 1-4.) 



Desmidium aculeatum Ehrenb. Inf. 1838, p. 142, t. 10, f. 12. 



Staurastrum aculeatum Menegh. Synops. Desm. 1840, p. 226 ; Ealfs, Brit. 



Desm. 1848, p. 142, t. 23, f. 2; Arch, in Pritch. Infus. 1861, p. 742 ; 



Rabenh. Krypt.-fl. Sachs. 1863, p. 194 ; Lund. Desm. Suec. 1871, p. 68 ; 



Jacobs. Desm. Danem. 1875, p. 207 ; Delp. Spec. Desm. subalp. 1877, 



p. 63, t. 13, f. 3-5 ; Kirchn. Alg. Schles. 1878, p. 166 ; Wolle, Desm. U. S. 



