COSMAEIUM. 89 



margins with one median undulation (one crest and 

 two hollows), apex broadly truncate or very slightly 

 retuse. Side view of semicell broadly elliptic-ovate. 

 Vertical view elliptic, ratio of axes about 1 : 1*9. 

 Cell- wall smooth. Chloroplasts axile, one in each 

 semicell, containing a central pyrenoid. 



Zygospore unknown. 



Length 10'6-11/x; breadth 9'5-9'S ^ ; breadth of 

 isthmus 1'4-2'5/x; thickness 5 //,. 



IRELAXD. Ballynahinch, G-alwav ! 



v u 



This small species stands near to the small Cosmarinm 

 described by Wille as " C. Mene<jliinii var. nanum" but 

 differs in its smaller size, its much deeper constriction, and 

 in the character of its cell-outlines. From C. umbilicatum 

 Liitkem. it is distinguished bv its much smaller size, its 



i> 



deeper constriction, and the absence of the scrobiculated 

 central protuberance. The form of its semicells, its small 

 size, and deep constriction are sufficient to readily dis- 

 tinguish it from C. Meneghinii. 



In Hoy, Orkney Islands, among- Sphagnum, a large form 

 was observed in which the apex was somewhat more retuse 

 and not quite so wide: length 16 /i; breadth 14 u (PL 

 LXXII, fig. 24). 



108. Cosmarium Regnellii TTille. 

 (PI. LXXII, figs. 25-28.) 



Cosmai-ium Regnellii Wille, Sydamerik. Algfl. 1884, p. 16, t. 1, f. 34; De 

 Toiii, Syll. Alg. 1889, p. 939; Tarn. Freshw. Alg. E. India, 1893, p. 49, 

 t. 7, f. 25, 26 ; Borge, Siissw. Chlor. Archang. 1894, p. 28 ; West & G. S. 

 West, Some N. Amer. Desm. 1896, p. 248, t. 15, f. 20; Xorclst. Index 

 Desm. 1896, p. 222 ; West & G. S. W T est, Alg. S. England, 1897, p. 487 ; 

 G. S. West, Alga-fl. Cambr. 1899, p. 216; West & G. S. West, Alga-fl. 

 Yorks. 1900, p. 93; Alg. X. Ireland, 1902, p. 35; Freslnv. Alg. Orkneys 

 and Shetlands, 1905, p. 22. 



Ursinella Regnellii Kuntze, Eevis. gen. plant. 1891, p. 925. 



Cells rather small, about as long as broad, deeply 



constricted, sinus verv narrowly linear with a slightly 



j *j *j 



dilated apex ; semicells trapezoid-hexagonal, lower 

 lateral margins longer than the upper lateral margins 

 and slightly retuse, upper lateral margins markedly 

 retnse, lateral angles projecting and rounded, slightly 

 upwardly divergent, apex broadly truncate. Side 

 view of semicell rounded -ovate. Vertical view sub- 



