270 .IJRITISH DESMEDIACE^. 



dilated extremity ; semicells truncate-pyramidate, 

 basal angles rounded, sides convex, apical angles 

 rounded, apex truncate or narrowly truncate; cell-wall 

 granulate ; granules very small, 24-29 showing on 

 eacli lateral margin, apex smooth, generally more or 

 less concentrically disposed towards the margin but 

 scattered in the centre of the semicells. Side view of 

 semicell very broadly elliptic. Vertical view elliptic, 

 ratio of axes about 1 : 1*5, granules disposed in indis- 

 tinct transverse series, smooth in the centre. Chloro- 

 plasts axile, with two pyrenoids. 



Zygospore unknown. 



Length 130-1 50 //,; breadth 98-105 /A; breadth of 

 isthmus 35-46'5/x; thickness 62'5/^. 



SCOTLAND.- -Ben Laoigh, Craig-an-Lochan, and Grlas 

 Mhoel, Perthshire ! 



This species occurred in bogs amongst numerous other 

 Desmids. It should be compared with C. pyramidal um Breb. 

 and C. pseudopachydermum Nbrdst., from both of which it 

 differs in the form of its semicells and in its finely granulate 

 cell- wall. 



224. Cosinarium tetraophthalmum Breb. 

 (PL XCV, figs. 4-7.) 



Cosmarium tetraophthalmum Breb. in Ralfs' Brit. Desm. 1848, p. 98, t. 17, 

 f. 11 [figures not accurate] ; t. 33, f. 8 ; Kiitz. Spec. Alg. 1849, p. 175 ; 

 De Bary, Conj. 1858, p. 54; Arch, in Pritch. Infus. 18(31, p. 732; 

 Babenh. Flor. Europ. Algar. Ill, 1868, p. 159 ; Delp. Desm. subalp. 

 1877, p. 26, t. 9, f. 1-4 [figures not acciirate] ; Klebs, Desm. Ostpreuss. 

 1879, p. 41 ; Boldt, Siber. Chloropliy. 1885, p. 108; Cooke, Brit. Desm. 

 1887, p. 99, t. 38, f . 1 "figure bad] ; Hansg. Prodr. Algenfl. Bohm. 1888, 

 p. 200; Boldt, Desm. Gronland, 1888, p. 28; De Toni, Syll. Alg. 1889, 

 p. 981 ; West, Alg. N. Wales, 1890, p. 289 ; Borg. Desm. Brasil. 1890, 

 p. 37 ; Ghitw. Flor. Glon. Okolic Lwowa, 1891, p. 51 ; West, Alg. W. Ire- 

 land, 1892, p. 151 ; Alg. Engl. Lake Distr. 1892, p. 726 ; Liitkem. Desm. 

 Attersees, 1893, p. 556 ; Eoy & Biss. Scott. Desm. 1894, p. 176 ; Nordst. 

 Index Desm. 1896, p. 253 ; West & G. S. West, Alg. S. England, 1897, 

 p. 488 ; G. S. West, Alga-fl. Cambr. 1899, p. 217 ; West & G. S. West, 

 Alga-fl. Yorks. 1900, p. 82 ; Bohlin, Flor. Algol, d'eau douce d. A9ores, 

 1901, p. 65 ; Borg. FresliAv. Alg. Faroes, 1901, p. 228 ; West & G. S. 

 West, Alg. N. Ireland, 1902, p. 37 ; Larsen, Freshw. Alg. E. Greenland, 

 1904, p. 89; West & G. S. West, Freshw. Alg. Orkneys and Shet- 

 lands, 1905, p. 21 ; Further Contrib. Plankton Scott. Lochs, 1905, 

 p. 485 ; Comp. Study Plankton Irish Lakes, 1906, p. 85 ; Borge, Beitr. 

 Alg. Schweden, 1906, p. 30. 



