COSMAEIUM. 231 



Length 24-31 /i; breadth 21-26 //,; breadth of isth- 

 mus 7*5-9'5/>t; thickness 17-1 9*5 /x. 



IRELAND.- -Creggan Lough, Galway ! 



Geogr. Distribution.- -Qalicia, in Austria. Nova 

 Zembla. Greenland. E. Africa. 



This variety approaches very closely certain forms of 

 C. subcostatum, a species with which it should be very care- 

 fully compared. It differs only in its central tumour, which 

 is much broader and furnished with 6-8 vertical series of 

 granules. There is only one pyrenoid in each chloroplast, but 

 the small forms of C. subcostatum have likewise but one 

 pyrenoid. 



201. Cosmarium subprotumidum K"ordst. 

 (PI. LXXXVI, figs. 19-21.) 



Cosmarium siibprotumidum Nordst. Desm. Ital. 1876, p. 38, t. 12, f . 14 ; 



De Toni, Syll. Alg. 1889, p. 1010 ; West, Danish Algae, 1891, p. 420 ; 



Alg. Engl. Lake Distr. 1892, p. 728 ; Nordst. Index Desm. 1896, p. 246 ; 



West & G. S. West, Alga-fl. Yorks. 1900, p. 77 ; Alg. N. Ireland, 1902, 



p. 39 ; Freshw. Alg-. Orkneys and Shetlands, 1905, p. 20 ; G-. S. West, 



Alg. Third Tanganyika Expedit. 1907, p. 121. 

 Ursinella subprotumida Ktintze, Revis. gen. plant. 1891, p. 925. 



Cells small, almost as broad as long, deeply con- 

 stricted, sinus narrowly linear ; semicells trapeziform- 

 snbsemicirciilar, lower third of equal width, upper 

 two-thirds strongly narrowed towards the apex, basal 

 angles rectangular and scarcely rounded, upwardly 

 converging parts of sides with two hollows and a 

 median crest, the latter generally retuse or retuse- 

 emarginate, apical angles obtuse or more frequently 

 obliquely retuse, apex truncate and with two or four 

 small undulations between the angles; cell-wall 

 furnished with more or less radially arranged 

 granules within the margin, generally in pairs just 

 within each crenation, but sino'le further away from 



o / 



the margin ; with a large granulated tumour in the 

 centre of the semicell above the isthmus, granules 

 arranged in 3 vertical series (4 or 5 granules in each), 

 the middle series straight (rarely duplicated) and the 

 outer series forming arcs. Side view of semicell ovate, 



o 



with a rounded apex and a large tumour near the base 



