144 BRITISH DESMIDIACE^. 



in the marginal region ; inner series often somewhat 

 reduced. 



Length 52-57'6^; breadth 40-45'(>/u; breadth of 

 isthmus 17-20-4 /i ; thickness 25-28'S M. 



SCOTLAND.- -Loch Ruthven, Inverness (Roy fy Bissett). 



Geogr. Distribution.- -Norway. Greenland. 



Forma polysticha nol). (PI. XCI, fig. 12.) 



C. hexastichum var. polystichum Boldt, Desmid. Gronland, 1888, p. 23. 

 C. supraspeciosum Wolle var. emarginatum West, Alg. Engl. Lake Distr. 

 1892, p. 729, t. 9, f. 24. 



Semicells with 10 or more parallel series of emargi- 

 nate warts in the marginal region ; inner two series 

 much reduced ; number of warts in each series 18-27. 

 Poles of vertical and side views with 10 or more 

 granules. 



Length 55'2-61/t; breadth 45'6-52/u; breadth of 

 isthmus 18-20-4/1. 



ENGLAND.- -Brothers' Water, Westmoreland ! 



Geogr. Distribution.- -Greenland. 



145. Cosmarium dovrense Nordst. 

 (PI. LXXVII, figs. 5, 6.) 



? Euastrum crenatum Perty Kleinst. Lebensf . 1852, p. 209, t. 16, f. 10. 

 Cosmarium crenatum var. subcrenatum Eabenh. Flor. Europ. Alg-. Ill, 



1868, p. 165. 

 Cosmarium dovrense Nordst. in Wittr. & Nordst. Alg. Exsic. 1879, no. 



255; fasc. 21, p. 40; De Toni, Syll. Alg. 1889, p. 947; Eacib. Desm. 



Nowe, 1889, p. 81, t. 5, f. 38 ; Lutkem. Desm. Attersees, 1893, p. 555 ; 



Nordst. Index Desm. 1896, p. 112 ; West & G. S. West, Alga-fl. Yorks. 



1900, p. 70. 



C. Perty anum Eacib. Nonn. Desm. Polon. 1885, p. 77. 

 Ursinella dovrensis Kuntze, Eevis. gen. plant. 1891, p. 924. 



Cells somewhat small, about 1-^- times as long as broad, 

 moderately constricted, sinus somewhat linear, but 

 not closed; semicells semi-elliptic (or subsemicircular), 

 about two-thirds of the circumference of a circle, some- 

 times a little narrowed at the base, basal angles sub- 

 rectangular but rounded, margin 8-crenate (or undulate- 

 crenate), rarely 10-crenate, crense 2-4-granulate, 



