LAMELL1DEXS 177 



Unio marginalis var. tricolor, H. & T., C. I. 1876, p. 20, pi. 42, 

 fig. 5. 



Original description : Testa valde inaequilatera, ellipfcica, tenera, 

 nitida, modice convexa, obsolete sulcata et subtilissime strigata, 

 olivaceo-f usca, parte inferiore flava ; postice laete viridi-radiata ; 

 umbonibus depressis ; area compressa ; dentibus cardinalibus 

 compressis, dextro duplicate, lamellis tenuibus acutis ; margarita 

 nitido-caerulescens, subtiliter radiata. 



Long. 28-25, lat. 60-5, diam. 17-25 mm. 



Kiister gives as the habitat of his species ' ; JEgypten im Nil," 

 but this must be an error, as the shell he figures is obviously 

 a variety of the Indian L. marginalis. It is represented in the 

 Indian Museum collection by specimens from the following 

 localities : Shuaygooinyo, Burma and Manbhoom, Bengal. 



Var. zonata (Deshayes). 



Unio marginalis, .Desh. Encycl. Meth., Vers. ii, p. 587. 

 Unio marginalis, Lk., var. zonata, H. & T., C. I. 1876, p. 20, pi. 44, 

 fig. 2. 



Shell oval, transverse, inequilateral, thin, covered with a dark 

 brown periostracum interrupted towards the margins by trans- 

 verse zones of rather pale greenish-yellow ; anterior side rounded, 

 obtuse, rather narrower than 'the posterior side which terminates 

 in a somewhat prominent angle ; the dorsal and posterior margins 

 compressed and slightly dilated in the form of a wing, separated 

 towards the umbones by a posterior angle continuing to the top, 

 interior of shell nacreous, rather deep and very bright yellow, 

 tinged with reddish and bluish shades towards the posterior side ; 

 hinge very narrow, gently arched, consisting, in the right valve, 

 of an oblong, crested, cardinal tooth roughened on the inner side, 

 crenellated at its free end and bearing on the outward side a small 

 decurrent swelling which limits the cavity into which the tooth 

 of the opposite valve is received ; left valve bearing two blunt 

 teeth, of which the posterior, which is the shorter, only commences 

 to rise at the extremity of the other ; lateral posterior tooth 

 elongate, arched, narrow, sharp, rough and truncated at its 

 posterior end, fitting between two lamellae in the left valve which 

 are unequal both in length and height. 



Long. 46, lat. 84 mm. 



Hau. Bengal. 



There are specimens which correspond to this description in the 

 Indian Museum collection from Rangoon, the measurements of 

 three of these being as below : 



1. 2. 3. 



Long 39-5 41 36 mm. 



Lat 74-5 73 67 mm. 



Diam. 23 19 23 mm. 



