BRITISH DESMIDIE^. 91 



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

 which answered the above description, 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, 

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

 a species, awaiting the result of further observations. 



Length of frond —^ of an inch ; breadth at base -^^ ; breadth of end yjo • 

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



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

 tracted beneath the end ; the end margin slightly concave. 



Euastrum? sublobatum, Brebisson, in lit. cum icone (1846). 



Machynlleth and Dolgelley, North Wales, J. R. Ambleside, Mr. Side- 

 botham. 



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. 



Euastrum 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 Cosmarium quadratum ; 

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

 cavities, inclines me to retain this species in Euastrum. 



Length of frond -g\^ of an inch ; breadth at base -^^ ; breadth at constric- 

 tion 3-2^5" ' breadth of end xoVs^. 



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 with 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 



