188 BRITISH 



broadly siibrhomboid-elliptic, ventral margin somewhat 

 more convex than dorsal margin, lateral angles rounded. 



O ' O 



Vertical view triangular, sides straight, angles broadly 

 rounded. Cell- wall granulate, grannies with no definite 

 disposition, and those at the angles modified to form 

 minute spines, with a smooth area at the apex of each 

 semicell. 



Zygospore globose, furnished with long spines, each 

 arising from a broadly conical base, and doubly furcate 

 at the apex. 



Length 34-35 p.; breadth 27-29 /x; breadth of isth- 

 mus 10-12'5/x; diam. zygosp. without spines 38 /x, 

 with spines 63-67 />t. 



ENGLAND.- -Near St. Just, Cornwall (with zy go- 

 spores) ! 



This species appears to connect the St. punchdatumspecies- 

 group with those forms possessing minute spines such as occur 

 in Staurastrum hirsutum. The zygosporeis exactly like those 

 of St. purictulatum var. pygmxum and St. punctulatum var. 

 striatum. The outward shape of the semicells and the form 

 of the vertical view are more or less in agreement with St. 

 punctulatum var. Kjellinani, hut the character of the granu- 

 lation is quite different, especially in the development of the 

 minute spines at the angles. 



39. Staurastrum granulosum (Ebrenb.) Ralfs. 

 (PL CXXVIII, figs. 10-12.) 



Desmidium granulosum Ehrenb. in Abh. Akad. Wiss. Berlin, 1839, pp. 51, 

 56, t. 1, f .' 12. 



Staurastrum granulosum (Ehrenb.) Ralfs, Brit. Desm. 1848, p. 217; Arch, 

 in Pritch. Inf us. 1861, p. 738 ; Rabenh. Flor. Europ. Alg. Ill, 1868, p. 

 206 ; De Toiii, Syll. Alg. 1889, p. 1147 ; Gut\v. Flor. glonow G-alic. 1892, 

 p. 134 ; ? Roy & Kiss. Scott. Desm. 1893, p. 238 ; 1894, t. 3, f. 6 ; W. & 

 G. S. West, Alg. N. Ireland, 1902, p. 45, t. 2, f . 24 ; Notes Alg. Ill, 

 1903, p. 76; Scott. Freshw. Plankton, I. 1903, p. 529; Freshw. Alg. 

 Orkneys and Shetlands, 1905, p. 24 ; Comp. Study Plankton Irish Lakes, 

 1906, p. 86 ; Hrit. Freshw. Phytoplankton, etc., 1909, p. 182. 



St. lunatutn Ralfs var. subarmatum W. & Gr. S. West, New Brit. Freshw. 

 Alg-. 1894, p. 10, t. 2, f. 47. 



Cells small, about as lonsf as broad, or sometimes a 



O * 



little longer, deeply constricted, sinus open and sub- 

 rectangular, with an indistinctly acuminate apex ; 

 semicells more or less obsemicircular, apex convex, 



