Dr. G. C. "Wallich on Desmidiacea from Lower Bengal. 281 



projection next the end lobe. The middle segment is nearly 

 simple and emarginate:" 



The prominent feature of var. /3 consists in its largely deve- 

 loped, triangular terminal lobe, the base of which is directed 

 outwards, emarginate at its angles and centre, and furnished 

 with two short stout teeth placed obliquely to each other, as in 

 M. Baileyi. The central emargination of this lobe is deep and 

 rectangular ; and the entire lobe projects but very slightly be- 

 yond the apices of the lateral ones. The margins of the filament 

 are parallel and direct; the fronds tabular, and divided by a 

 very deep constriction into two dichotomously incised segments, 

 the ultimate subdivisions of which are emarginate. 



In the Bengal variety, the " tooth-like projections" next the 

 terminal lobe are acutely angular, instead of being rounded; 

 and, as in the case of Onychonema, the projecting processes, by 

 which cohesion is either secured or increased, overlap each other 

 alternately in adjacent fronds. 



M. foliacea, var. /3, occurs abundantly in some localities, and 

 invariably in the condition described. Seen under the micro- 

 scope, the rich emerald-green filament is, without exception, the 

 most beautiful of the Desmidiacese. 



Length of frond -0033" ; breadth -0028". Diameter of spo- 

 rangium, exclusive of spines, f 0018". 



Lower Bengal, 1855. 



Plate XIV. fig. 1. Front view in filament. Fig. 2. End view. Fig. 3. 

 Basal view of segments. Fig. 4. Sporangium. 



***** Frond cruciform. 



7. M. cruciata, n. s. Frond cruciform, divided by a concave 

 notch into two dichotomously-furcate, symmetrically-lobed 

 segments. 



The two curious forms placed under this section are so ano- 

 malously constructed as to render it doubtful whether they 

 really belong to the genus under notice. The absence of all 

 trace of a central suture is remarkable ; and in this respect they 

 resemble some species of Penium. M. cruciata cannot be better 

 described than by likening it to the four terminal lobes of M. 

 furcata united together by their bases, the intermediate angles 

 being completely rounded off. Like the lobe of that species, 

 each extremity is furcate ; the branches curved inwards. The 

 apices are tridentate. 



Diameter of frond -0019". 



. Lower Bengal, 1855. 



Plate XIII. fig. 12. Front view. 



8. M . pusilla. Frond cruciform, divided by a concave notch into 

 Ann. $ Mag. N. Hist. Ser. 3. Vol. v. 19 



