178 BRITISH DESMIDIACE/E. 



Cell- wall finely granulate, granules arranged in rings 

 around the angles, although sometimes a little scattered 

 on the body of the semicell, granules at the end of 

 each angle often a little larger than the rest. 



Zygospore compressed, having a circular outline in 

 the front view, with 10-12 marginal undulations ; side 

 view oblong. 



Length 19-28/x; breadth 18-28 /*; breadth of isthmus 

 6-10 /^; diam. zygosp. 35-39 JJL, thickness 21-24 p.. 



WALES. Capel Curig and near Bethesda, Carnar- 

 vonshire ! 



IRELAND.- -Near Westport, Louisburgh, and Dugort, 

 Mayo ! Near Leenane, Roundstone, and Ballynahinch, 

 Galway ! 



Geogr. Distribution. Germany. Galicia in Austria. 

 Hungary. Norway. Sweden. India. Australia. 

 New Zealand. Azores. United States. Brazil. 

 Patagonia. 



St. striolatum differs from St. dilatafum in the outward 

 form of its semicells and its somewhat different granulation. 

 As in St. disputatum the semicells have a fiat apex, but the 

 granulation extends over the whole body of the Staurastrum. 



We can see no valid reason for the separation of Wittrock's 

 var. oelandicum, the characters of which were based upon the 

 zygospore. This is, however, similar in every respect to other 

 zygospores which must be attributed to St. striolatum. 



We figure the following variety for comparison with the 

 more typical forms of St. striolatum : 



Var. DIVERGENS nob. \_St. altemans var. divergens W. & 

 Gr. S. West, Freshw. Alg. Ceylon, 1902, p. 177, t. 21, f. 18.] 

 Cells a little smaller, apices of semicells concave, angles very 

 faintly dilated (indistinctly subcapitate) and slightly divergent; 

 angles of one semicell alternating with those of the other. 

 Length 17 ^u ; breadth 17-18^; breadth of isthmus 5'5//. 

 (PL CXXVII, fig. 6.) Distrib. Ceylon. 



35. Staurastrum rugulosum Breb. 

 (PI. CXXVI, fig. 3.) 



Staurastrum rugulosum Breb. in Ralfs' Brit. Desm. 1848, p. 214, t. 35, 

 f. 19; Arch, in Pritch. Infus. 1861, p. 740 ; Babenh. Flor. Europ. Alg. 

 Ill, 1868, p. 208; Kirchn. Alg. Schles. 1878, p. 164; De Toni, Syll. 



