EUASTKUM. 35 



Cells very small, about twice as long as broad, 

 oblong-elliptic in outline, deeply constricted, sinus 

 narrowly linear and dilated at the extremity ; semi- 

 cells semi-elliptic, with four undulations up each side 

 and an emarginate apex. Side view of semicell ovate- 

 elliptic ; vertical view elliptic. Cell-wall smooth. 



Zygospore unknown. 



Length 23-27 p.; breadth 12-15 /* ; breadth of 

 isthmus 4 ^ ; thickness 6-8 JJL. 



Geo'/r. Distribution. Germany. Galicia in Austria. 



The typical form of this species is unknown in the British 

 Islands. Ghitwinski gives as the measurements of his Austrian 

 specimens : length 29 ^ ; breadth 17 fj. ; breadth of isthm. 7 /m. 

 The figure we give is exceedingly poor, but as it is an exact 

 copy of Reinsch's original, this could only be expected. 



Var. latius Roy & Biss. 



E. Sendtnerianum var. latius Eoy & Biss. Scott. Desm. 1893, p. 177; 

 Nordst. Index Desm. 1896, p. 232. 



Larger than the type, with broader apices. 



Length 43*2 ^ ; breadth at base of semicells 25'6 //,, 

 at apex 19*2 p.. 



SCOTLAND. Near Den of Maidencraig, Aberdeen 

 (Eon Bissett). 



We are unacquainted with this variety and are unable to 

 give a figure of it. 



21. Euastrum rostratum Ealfs. 

 (PI. XXXVII, figs. 11-13.) 



Euastrum rostratum Ealfs ill Ann. Mag. Xat. Hist. 1844, p. 192, t. 7, f. 5; 



Hass. Brit. Freshw. Alg. 1845, p. 382, t. 91, f . 8 ; Ralfs, Brit. Desm. 



1848, p. 88, t. 14, f. 6 ; Arch, in Pritch. Infus. 1861, p. 730, t. 1, f. 26 ; 



Cooke, Brit. Desni. 1886, p. 73, t. 35, f. 2 (figures partly copied from 



Ealfs, and bad) ; De Toni, Syll. Alg. 1889, p. 1099 ; ? West, Freshw. 



Alg. W. Ireland, p. 138; Eoy & "Biss. Scott. Desm. 1893, p. 177; 



West & G. S. West, Alg. S. England, 1897, p. 483; Alga-fl. Yorks, 



1900, p. 62. 



E. elegans b. rostratum Rabenh. Flor. Europ. Algar. Ill, 1868, p. 186. 

 Helierella rostrata Kuntze, Eevis. gen. plant. 1891, p. 899. 



Cells small, a little more than 1-| times longer than 

 broad, very deeply constricted ; sinus narrowly linear, 



