58 BRITISH DESM1DIACE.E. 



compelled to give it a new name owing to the existence of a 

 Burmese Euastrum which was described by Joshua in 1886 

 as E. exile. 



34. Euastrum incavatum Josli. & Xordst. 

 (PI. XXXIX, figs. 6, 7.) 



Euastrum incavatum Josh. & Nordst. in Wittr. & Nordst. Alg. Exsic. no. 

 657, 188-4, c. fig. xylogr ; Josh. New and Kare Desm. 1885, p. 33, t. 254, 

 f. 1 ; De Toni, Syll. Alg. 1889, p. 1075 ; West, Alg. N. Yorks. 1889, 

 p. 292 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 65. 



Helierella incavata Kuntze, Revis. gen. plant. 1891, p. 898. 



Cells small, If times longer than broad, very deeply 

 constricted, sinus narrowly linear ; semicells pyra- 

 midate from a dilated base, basal angles rounded or 

 somewhat obliquely truncate, gradually attenuated to 

 the apex, which is dilated, upper part of lateral margins 

 retuse, apical angles acute and horizontally subapicu- 

 late ; apex convex, suddenly and deeply retuse in the 

 middle ; semicells with a small tubercle within each of 

 the basal and apical angles. Side view of semicell 

 ovate. Vertical view elliptic. Cell- wall smooth. 



Zygospore unknown. 



Length 35-43 ^ ; breadth 20-24 JJL; breadth of 

 isthmus 4'5-6/x,; thickness 14-16 p.. 



ENGLAND.- -Mickle Fell, X. Yorks ! 



Geoqr. Distribution. United States. W. Indies 



/ 



(Jamaica). 



AVe have only observed this small species on one occasion. 

 It is sharply defined by reason of its relatively great length 

 and its peculiar apex. 



35. Euastrum montanum West & Gr. S. West. 



(PL XXXIX, figs. 8, 9.) 



Cosmarium Meneghinii Breb. forma, Boldt, Desmid. Gronland, 1888, p. 13, 



t. 1, f. 15. 



C. Meneghinii forma Boldtii West, Alg. Eng. Lake Distr. 1892, p. 726. 

 C. Subreinschii Sehmidle var. Boldtiana Schmidle in Flora, 1894, p. 90, 



t. 6, f. 8 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 80 ; Alg. N. Ireland, 



1902, p. 36. 

 Euastrum montanum West & G. S. West, Freshw. Alg. Ork. and Shetl. 1905, 



p. 14 (sep.), t. 1, f. 11, 12. 



Cells very small, a little more than 1^ times longer 

 than broad, deeply constricted, sinus narrowly linear 



