EUASTRUM. 71 



lobes widely subrectangular ; polar lobe broadly rect- 

 angular, angles rounded, apex convex with a strong 

 median thickening; lateral lobes short, angles rounded, 

 outer margins retuse ; semicells with a central papillate 

 protuberance. Side view of semicell elliptic, with an 

 acute papilla at the middle on each side. Vertical view 

 elliptic, with an acute papilla at the middle on each 

 side. Cell-wall smooth and slightly thickened at the 

 base of all the sinuations. 



Zy go spore unknown. 



Length 24 ^ ; breadth 1 5 JJL ; breadth of isthmus 

 3*8 JJL; thickness 11 '5 /x. 



EXGLAXD. Xear Senens, Cornwall ! 



This species forms one of the connecting links between the 

 genera Euastrum and Cosmarium. There is no actual emar- 

 gination of the apex of the semicells, although there is a 

 thickened internal ridge occupying its place. It might 

 equally well be called Cosmarium Cornubiense West & Gr. S. 

 West. 



43. Euastrum crassicolle Lund. 

 (PL XL, figs. 9, 10.) 



Euastrum crassicolle Lund. Desm. Suec. 1871, p. 23, t. 2, f. 8; West, Alg. 



X. Wales, 1890, p. 288 ; Boy & Biss. Scott. Desm. 1893, p. 176 ; Xordst. 



Index Desm. 1896 ; West & G-. S. West, Alga-fl. Yorks. 1900, p. 65. 

 E. crassicolle a. typicum Racib. Nonn. Desni. Polon. 1885, p. 91. 

 Helierella crassicollis Kuntze, Eevis. gen. plant. 1891, p. 898. 



Cells minute, about twice as long as broad, deeply 

 constricted, sinus narrowly linear ; semicells truncate- 

 pyramidate, almost three-lobed ; polar lobe prominent, 

 wide, slightly dilated, angles rounded, apex emarginate ; 

 lateral lobes very short, somewhat bilobulate with 

 rounded angles. Side view of semicell oblong-pyra- 

 midate, apex truncate, lateral margins towards the 

 base biundulate. Vertical view elliptic, poles truncate, 

 and with a broad inflation at the middle on each side. 

 Cell- wall smooth. 



Zygospore unknown. 



Length 24'5-28/x; breadth 13'5-15/x; breadth of 

 isthmus 5'2-8'5/x; thickness 9*5-11 p. 



EXGLAXD. Mickle Fell, X. Yorks ! 



