164 BRITISH DESMIDIACEJE. 



other part of the British Islands. Bissetfc published no des- 

 cription of the species and only a very poor figure, but in 

 1894 Messrs. Roy and Bissett published an excellent figure 

 in their ' Scottish Desmids' (pi. 2, f. 15). We have found it 

 in several parts of the British Islands, but never in abundance. 



C. Logiense should be compared with C. reniforme, from 

 which it is distinguished by its proportionately greater length 

 and by the smaller size of the granules. The semicells are of 

 a different form from those of C. reniforme, and the apex of 

 the sinus is not so dilated. 



In 1899 Borge described and figured what he imagined to 

 be typical C. Logiense. He had evidently overlooked the 

 figure published by Messrs. Roy and Bissett, and his Cuban 

 specimens (vide Borge, ' Trop. u. subtrop. Sussw.-Chlor/ 1899, 

 p. 19, t. 1, f. 21) represent some other Desmid, possibly a 

 form of C. pulchellum Turn. 



158. Cosmarium granulatum West. 

 (PI. LXXX, fig. 3.) 



Cosmarium granulatum West, Alg-. N. Yorks. 1889,, p. 292, t. 291, f . 4 ; 

 Nordst. Index Desm. 1896, p. 134 ; West & G. S. West, Alga-fl. Yorks. 

 1900, p. 72. 



Cells large, deeply constricted, sinus narrowly linear, 

 very slightly dilated at the extremity and opening out- 

 wards ; semicells very broadly elliptical with a rather 

 flattened base, sides and apex much rounded. Side view 

 of semicell elliptic. Vertical view elliptic and slightly 

 compressed. Cell-wall finely granulate, granules very 

 small and flattened, causing the margin of the semicell 

 to be minutely undulate, those granules near the 

 margin arranged in concentric series, those in the 

 central part of the semicell irregularly disposed and 

 reduced in size. 



Zygospore unknown. 



Length 125^; breadth 85/x; breadth of isthmus 

 25 /x, ; thickness 50 ^. 



ENGLAND.- -Crook Grhyll near Buckden, W. Yorks 1 

 Cronkley Fell, K Yorks ! 



This species is readily distinguished by the form of its 

 semicells and its minute granulation. We have not observed 

 any living specimens and are therefore unable to describe 

 the chloroplasts. 



