COSMARIUM. 269 



and often curved marginal spines in place of the conical 

 granules of C. ovale, and is known to occur in Australia, Brazil, 

 and Uruguay. The latter is the largest known species of the 

 genus (length 255-260 /.t ; breadth 174-176 /LI), and the conical 

 granules of C. ovale are in this case replaced, except for a 

 few spines at the base, by several series of emarginate warts. 

 This large Desmid is at present only known from Paraguay. 



Ealfs' figure of C. ovale in his ( British Desmids/ 1848, 

 t. 15, f. 9, is not very accurate. The marginal granules are 

 not so broad as he figures them, but more conical, and they 

 never extend regularly over the extreme apex of the semi- 

 cell ; neither are they disposed in such a regular band as he 

 portrays them in his figure of the side view. 



The marginal granules or teeth are solid, and very fre- 

 quently they have a decided upward curve such as is more 

 distinctly evident in the short spines of C. denticulatum. 



C. ovule occurs chiefly in the western British areas, more 

 especially in the old bogs, but it is very local although some- 

 times fairly abundant. It occurs in the plankton of the 

 western lake-areas. 



Var. subglabrum West & G. S. West. (PL XCIV, 



fig. 11.) 



C. ovale var. subglabrum West & G. S. West, Some N. Amer. Desin. 1896, 

 p. 249, t. 15, f. 3 ; Alg. S. England, 1897, p. 488. 



Cells a little smaller than in the type, lateral margins 

 of semicells minutely undulate ; grannies few, about 2 

 (rarely only one) at each basal anoie, 3-4 at the 



t/ O 



margin just below the apex and 1-3 within the margin 

 near the apex ; apex narrowly truncate. 



Length 154/x; breadth 88 p. ; breadth of isthmus 

 30 p. 



ENGLAND.- -Xew Forest, Hants ! 



Geogr. Distribution.- -United States. 



223. Cosmarium Scoiicum West & G. S. West. 



(PI. XCV, figs. 1-3.) 



Cosmarium Scoticum West & G. S. West, New Brit. Fresliw. Alg. 1894. 

 p. 6, t. 1, f. 23 ; Nordst. Index Desm. 1896, p. 230. 



Cells very large, about 1-J- times as long as broad, 

 deeply constricted, sinus narrowly linear with a 



