Dr. G. C. Wallich on Desmidiacea from Lower Bengal. 279 



frond, however, is minutely granulate, the segments are only 

 three-lobed, and the end lobe is more exserted than it is in those 

 species. The basal lobes are deeply partite, the end one is 

 merely sinuated. All the subdivisions are bidentate at the 

 apex." And lastly, M. ringens is thus described by Prof. Bailey 

 (' Smithsonian Cont., Microscop. Observations in South Carolina 

 and Georgia/ p. 37) : " Oblong ; segments 3-lobed, coarsely gra- 

 nulated near the edge ; basal lobes subdivided by a deep notch 

 into two rather broad and obtuse or slightly bidentate projec- 

 tions j terminal lobes exserted, emarginate ; extremities bidentate 

 or obtuse. Resembles M. Bailey i, Ralfs, but is larger, its divi- 

 sions less slender, and with the granulations differently placed." 



In var. 7, the lateral lobes are nearly horizontal, the outer 

 sub-lobe being exserted from the basal line of the segment, so 

 as to give a gaping appearance to the emarginate portion. The 

 terminal lobe is stout ; and from the base of its bifurcations, and 

 placed diagonally to each other, on opposite surfaces of the 

 frond, are given off the two additional processes referred to. It 

 is possible that, owing to the doubling down of these processes 

 (which it will be observed are perpendicular to the plane of the 

 frond), the impression of the ordinary processes being bifid at 

 their extremities may have arisen, as is stated to be the case in 

 the description of M . morsa (British Desmid. p. 74). The apices 

 of the furcations, as well as the extremities of the lateral sub- 

 lobes, are elongated and tridentate. 



Length -0060"; breadth -0048". 



Lower Bengal, 1855. 



Plate XIII. fig. 10. Front view. 



*** Lateral lobes deeply and equally tripartite. Subdivisions plane, 



3. M. alata, n. s. Frond rather longer than broad. Segments 

 deeply 3-lobed; lateral lobes deeply and equally tripartite; 

 terminal lobe furcate, and much exserted. 



This species appears to hold an intermediate position between 

 the American species M. Torreyi f described in the Appendix 

 to the { British Desmidicse/ and M. furcata. 



The deeply and equally tripartite form of the lateral lobes 

 distinguishes this very graceful species from all the allied ones. 

 The inner half of the terminal lobe, which is constructed on the 

 same plan as that of M. furcata, is very slender, and is received 

 into a deep notch formed by the two lateral lobes. Its furcate 

 ends are delicate, elongated, and project obliquely outwards, 

 without any perceptible curve. At the base of the furcation, the 

 margin is minutely punctate. The rest of the frond is perfectly 

 smooth. The lateral lobes are attached to the base of the seg-> 

 ment by a narrow isthmus, and at once expand to their full 



