Dr, G. C. Wallich on Desmidiacea from Lower Bengal. 283 



This species interferes with the distinction laid down by Mr. 

 Ralfs (British Desmid. p. 78) between Euastrum and Micrasterias, 

 inasmuch as the lobes are most distinctly incised, and radially 

 arranged. 



Length -0028"; breadth -0025". 



Lower Bengal, 1855. 



Plate XIV. fig, 8. Front view. Fig. 9. End view. Fig. 10. Side view. 

 Fig. 11, Basal view of segment. 



3. E. crassum, Breb. 



** Segments sinuated ; terminal lobe exserted and united with 

 the basal lobe by a distinct neck. 



4. E. numerosum. 

 E. affine, Ralfs. 



The transverse views of these two forms merge one into the 

 other. 



5. E. didelta, Turp. 

 E. ansatum, Ehr. 



The sporangium of these two varieties is tuberculate, 



**# frond without a distinct terminal lobe, and frequently with 

 a process, an acute angle/' or an inflation " at the corners of 

 the terminal portion " 



6. E. rostratum, Ralfs. 



Var. /3. Frond oblong. Segments sublobate, their lateral mar- 

 gins sinuate. Terminal margin notched and angular. 



The Bengal varieties occur in every intermediate form be- 

 tween E. elegans, which merges into E, rostratum on the one 

 side, and the small subangular E. binale on the other ; the latter 

 being indistinguishable from a variety of Cosmarium Meneghini. 

 Indeed it is far from improbable that E. elegam, E. binale, and 

 E f rostratum are only varieties of one typical species. 



7. E. turgidum, n. s. Frond large. Segments broadly euneate, 

 truncate, with a large central inflation. Terminal margin 

 straight. 



As seen in the front view, the general outline of this species 

 resembles that of the immature state of the large variety of 

 Xanthidium armatum. It is distinguished from it, however, by 

 the presence of the large central granulate inflation, the exist- 

 ence of a minute terminal notch, and by its not presenting the 

 characteristic funnel-shaped processes which are distributed sym- 

 metrically upon the frond in that species, 



It also bears some resemblance to the species recently dis- 

 covered in Ireland by the Rev. R. N. Dixou, and described under 



19* 



