BRITISH DESMIDIE^. 91 



that species ; for iu Dr. Dickie's specimen I observed a frond, one segment of 

 which answered the above descri})tion, whilst the other had a distinct, cuneate, 

 terminal lobe, as in E. crassum. But as I lost the frond before I was able to 

 obtain a satisfactory view of it, and as the form here described is so peculiar, 

 aiid has been noticed in widely separated stations, I have given it the rank of 

 a species, awaiting the result of further obsenations. 



Length of frond -^^ of an inch ; breadth at base ^^-o '■> breadth of end -^. 



Tab. XXXII. fig. 3. a. frond with endochrome ; b. transverse view. 



18. E.} siiblobatum (Breb.) ; segments subquadrate, somewhat con- 

 tracted beneath the end; the end margin slightly concave. 



Euastriun? sublobatum, Brcbisson, in lit. cum icons (1846). 



INIachpilleth and Dolgelley, North Wales, /. B. Ambleside, Mr. Side- 

 bo f ham. 



Falaise, Brebisson. 



Frond twice as long as broad, and rather larger than that of E. elegans ; 

 the segments nearly quadrate, their sides and end somewhat sinuated, and their 

 base slightly inflated. 



Euastrutn sublobatum has nearly as good a claim to a place in Cosmarium 

 as in this genus. The terminal notch is here replaced by a slight concavity, 

 and in their form its segments are not unlike those of Cosmariiim quadratum ; 

 but their constricted appearance, from the more strongly-marked lateral con- 

 cavities, inclines me to retain this species in Euastrum. 



Length of frond y^r ^^ ^^^ ^^^^^ ' bi'eadth at base -^\^ ; breadth at constric- 

 tion 3 ^^ g ; breadth of end yoVs"* 



Tab. XXXII. fig. 4. a. frond with endochrome ; b. empty frond ; c. trans- 

 verse view ; d. end view. 



8. COSMARIUM, Corda. 



Frond simple, constricted in the middle ; segments as broad as or 

 broader than long, neither sinuated nor notched. 



The fronds are minute, simple, constricted in the middle ; the seg- 

 ments are generally broader than long and inflato-compressed, but in 

 some species orbicular or cylindrical ; they are neither emarginate at 

 the end nor lobed at the sides, and have no spines or processes. 



Ehrenberg united plants belonging to this genus w^ith others having 

 lobed segments, in order to form his genus Euastrum. Meneghini 

 for the most part followed this arrangement, merely changing the 

 name to Cosmarium, which had a prior claim, and also adding some 

 species taken from Xanthidium. Under Micrasterias, Euastrum, and 

 Xanthidium, I have given my reasons for differing from such high 



