Dr. G. C. "Wallicli on Desmidiacea from Lower Bengal. 277 



variety of M. expansa, none of the differences amounting to 

 anything more than those of degree. The furcate processes are 

 longer, tlie margins arc serrate, the extremities of the basal 

 lobes and furcations are tridentate instead of being bidentate, 

 and the whole frond is somewhat longer. The basal lobe is 

 broadly fusiform, and gradually tapers to subacute apices. The 

 terminal lobe is short and linear as far as the furcation, and, 

 with the basal lobe, is furnished with a submarginal row of 

 short stout spines. 



Length -0050"; breadth -0045". 



Lower Bengal, 1855. 



Plate XIII. fig. 9. Front view. 



** Terminal lobes bifurcate. Furcations at right angles to each 



other. 

 2. M. morsa, Ralfs*. 

 M. Baileyi, llalfs. 

 M. 7'ingens, Bailey. 

 Var. S. Frond oblong. Segments three-lobed. Lateral lobes 

 deeply emarginate, inciso-serrate. Terminal lobe bifurcate. 



On comparing the general outline and structure of var. S with 

 what we find in M. morsa, as described and figured by INIr. llalfs, 

 it will, I think, be admitted that, however distinct, at first sight, 

 the Bengal form may appear to be, it presents no distinct cha- 

 racter of sufficient importance to demand its elevation into a 

 separate species. As regards M. Bailei/i and M. ringens, it is 

 difficult to speak so confidently; for in these we only meet with 

 the first-named ground for amalgamation. This is, however, by 

 no means unimportant ; and, coupled with the fact that in ' The 

 American Journal of Science and Arts^ (vol. xli. No. 2) Prof. 

 Bailey has figuied, although somewhat rudely and without any 

 appended description, a form exhibiting the bifurcate peculiarity 

 in question, })reviously obtained from the same habitat, and 

 otherwise agreeing with the general characters of the variety 

 under notice, it appears highly probable that M. ringens and 

 M. Baileyi arc identical with each other, and only constitute a 

 variety of M. morsa. 



Var. S is distinguished from M. morsa by its narrow lateral 

 lobes, in their being deeply emarginate, and in the terminal lobe 

 being much exserted. But it will be seen that these constitute 

 only differences as to the degree of certain features, which admit 

 of variation from climatic or accidental causes. So long as such 



* In the list of enata to the ' British Desmidieac,' the following in- 

 structions occur : — " Fur M. morsa read M. americana, Ehr., ami add the 

 following syiionym : Euastruin umericaiuua, Elir., Verl)ri!itiuig and Einiluss 

 des Mikros. Lcbens in Slid- and Nord-Amerika, t. \. f. 15, 18-lJ." The 

 characters, however, remain unaltered. 



