COSMARIUM. 139 



Length 68-73 p. ; breadth 53-55 /x ; breadth of isth- 

 mus 16-21 /A; thickness 26-29 (JL. 



WALES. Snowdon, Carnarvonshire (at 3,000 ft.) ! 

 SCOTLAND.- -Ben Laoigh, Perthshire ! 



Compared with its breadth this variety is proportionately 

 longer than any of the other varieties of C. Lundellii. 



Var. corruptum (Turn.) West & Gr. S. West, (PI. 



LVII, figs. 5, 6.) 



Cosmarium corruptum Turn. Freslrvv. Alg. E. India, 1893, p. 51, t. 8, f. 2. 

 C. subcirculare Turn. var. rugosum Turn. 1. c. p. 52, t. 8, f. 7. 

 C. rotundum Turn. I.e. p. 58, t. 8, f. 48. 



C. Lundellii Delp. var. corruptum (Turn.) West & G. S. West, Freshw. 

 Alg. Ceylon, 1902, p. 162. ' 



Cells smaller, sinus often somewhat open towards 

 the exterior ; cell-wall with variable scrobiculations of 

 small size, generally larger and more distinct near the 

 margin ; apex of semicells slightly subtruncate. 



Length 51-63 ^i; breadth 48*5-61^; breadth of 

 isthmus 23-28*5 /x. 



ENGLAND. Bowness, Westmoreland ! 



Geogr. Distribution. Gralicia in Austria. India. 

 Ceylon. 



This variety only differs from typical C. Lundellii in its 

 somewhat smaller size and in the greater distinctness of the 

 scrobiculations near the margins of the semicells. The sinus 

 is generally closed in its median part., although dilated at its 

 extremity and opening considerably towards the exterior. 



The plants named by Turner Cosmarium corruptum, C. sub- 

 circulare var. rugosum, and C. rotundum, are most certainly 

 forms of one species, and we have thought it best to place 

 them as a variety of C. Lundellii under the name "cor- 

 ruptum." 



C. Lundellii var. corruptum should be compared with C. 

 galeritum Nordst., from which it can be distinguished by its 

 wider and more depressed semicells,, with less truncate apices, 

 and by its much broader isthmus. 



6. Cosmarium pachydermum Lund. 

 (PI. LVII, fig. 7.) 



Cosmarium pachydermum Lund. Desm. Suec. 1871, p. 39, t. 2, f. 15; 

 Kirchn. Alg. Schles. 1878, p. 149; Wolle, Desm. U.S. 1884, p. 70, t. 15, 



