282 Dr. G. C. Wallich on Desmidiacea from Lower Bengal. 



two broad emarginate lobes, the angles of which are inflated 

 and bidentate. 



In like manner with the former species, this minute form 

 presents no visible central suture, but, on the contrary, is some- 

 what inflated at the central portion. Both may be young states 

 of other species ; but they did not occur in sufficient number to 

 enable me to decide the point. They are therefore placed pro- 

 visionally under Micrasterias. 



Diameter -0010". 



Lower Bengal, 1855. 



Plate XIII. fig. 13. Front views. 



10. Euastrum, Ehr. 



Frond compressed, deeply divided into two segments, which 

 are sinuate, lobed, emarginate, or furnished with inflated, often 

 granulated, protuberances. 



* Terminal lobe cuneate, included between the lateral lobes. 

 1. E. verrucosum, Ehr. 



Var. ft. Segments closely approximate along the entire bases. 

 Outer subdivision of lateral lobe parallel with the margin of 

 the terminal one, from which it is separated by a deep but 

 narrow notch. Lobes subradiate. 



This variety differs from the typical E, verrucosum in having 

 the margin of the terminal lobe straight and deeply incised, in 

 not being quite so turgid at the base of the segments, and in 

 wanting the terminal inflation represented as being present in 

 the British species. But in all other points the structure is 

 sufficiently similar to indicate that it is only a variety of that 

 form. 



Length -0031" ; breadth -0029". 



Lower Bengal, 1855. 



Plate XIV, fig. 5. Front view. Fig. 6. Side view. Fig. 7. End view. 



2. E. orbiculare, n. s. Frond orbicular. Lateral segments di- 

 vided into two equal portions by a deep incision. Lobes and 

 sub-lobes radiate. 



The orbicular outline of this species at once distinguishes it 

 from its allies, and more especially from the two forms of the 

 last-mentioned species. The terminal lobe, which is closely 

 embraced by the lateral sub-lobes, is deeply incised, and, coupled 

 with the incisions of the lateral lobes, imparts to the entire 

 frond a crenate and radiate character. 



The side- and end-views are very similar to those of var. fB of 

 E. verrucosum. 



