COSMARIUM. 181 



Cells small, a little longer than broad, deeply con- 

 stricted, sinus narrow, opening outwards ; semicells 

 truncate-subpyramidate, lower half of sides rounded, 

 upper half markedly retuse, apex widely truncate and 

 straight, upper angles sharp and rectangular. Side view 

 of semicell ovate, upper part of sides retuse. Vertical 

 view elliptic, inflated at the middle on each side. Cell- 

 wall smooth. Chloroplasts axile, with one pyrenoid. 



Zy go spore unknown. 



Length 22'5-24/x; breadth 19-19-5 JA; breadth of 

 isthmus 6-7 ^; breadth of apex 9-1 2 /x; thickness 

 12-13 p,. 



IRELAND. Ballynahinch, Galway ! 



Geof/r. Distribution. Austria (var.) and Galicia. 

 Poland. Central Africa. United States. Brazil (var.). 



This species hears some resemblance to C. retumm (Perty) 

 Rabenh., but the latter is larger,, more deeply constricted, 

 with a more produced apical part of the semicells, which is 

 not so wide, and is also sparsely furnished with granules. 

 C. retusifonne differs from C. Hammeri in its more open sinus, 

 its abruptly-truncate apex, its sharp superior angles, and in 

 its smaller size. 



37. Cosmarium Hammeri Reinsch. 

 (PL LXII, figs. 20, 21.) 



Cosmarium Hammeri Eeinsch, Spec. Gen. Alg. 1867, p. 115, t. 22 B, I, 

 f. 1-10 [inclusive of A. majus and B. intermedium^ ; Lund. Desm. 

 Suec. 1871, p. 37 ; Wolle, Desm. U. S. 1884, p. 79, t. 18, f. 27 ; Cooke, 

 Brit. Desm. 1886, p. 81 ; Hansgirg, Prodr. Algenfl. Bohm. 1888, p. 194; 

 De Toni, Syll. Alg. 1889, p. 936 ; West, Alg. N. Wales, 1890, p. 288 ; 

 Alg. W. Ireland, 1892, p. 142; Alg. Eng. Lake Distr. 1892, p. 724; 

 Eoy & Biss. Scott. Desm. 1894, p. 103 ; West & G. S. West, Some 

 N. Amer. Desm. 1896, p. 245 ; Norclst. Index Desm. 1896, p. 137 ; West 

 & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 74 ; 

 Alg. N. Ireland, 1902, p. 32. 



Didymidium (Cosmarium) Hammeri A. majus Eeinsch, Algenfl. Frank. 

 1867, p. Ill, t. 10, f. 1. 



Euastrum Hammeri Cohn, Desm. Bong. 1879, p. 270. 



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



Cells of moderate size, about 1 J times longer than 

 broad, subhexagonal, deeply constricted, sinus narrowly 

 linear with a dilated apex, opening outwards ; semi- 

 cells truncate-pyramidate, basal angles well rounded, 



