102 Records of the Indian Museum. [Voi,. XXIV, 



As a result of a careful examination of Tapperone-Canefri's 

 type-specimen of the species and the forms with which Simpson in- 

 cluded it, I am of opinion that Simpson's conclusions are quite 

 untenable. Not only is the species quite distinct from Benson's 

 Unio triembolus, but it also has no relationship whatsoever with 

 Gould's Unto tavoyensis. It is on the other hand to be grouped 

 with species like U. bhamoensis and U. mandelayensis, forms in 

 which the anterior margin is greatly shortened, the beak placed 

 far forwards and the posterior side drawn out into a cuneate or 

 elliptical lobe. The species may be redescribed as follows : — 



Shell subrhomboidal to subovate, moderately inflated, subsolid, 

 inequilateral; beaks high and full, very forwardly placed and 

 recurved outwards and downwards, with a fairly deep cavity, 

 sculptured irregularly with low zigzag transverse bars extending 

 over a little more than the depth of the shell ; posterior ridge only 

 feebly marked ; dorsal margin slightly arched, somewhat truncate ; 

 anterior margin very short, rapidly curving inwards between the 

 umbones in the lunule region and regularly curving below over the 

 podium to meet the nearly straight or slightly arcuate ventral 

 margin ; posterior margin longer than the anterior, sharply trun- 

 cate and rather slanting ; epidermis dark brown to black, some- 

 what shining ; ligament prominent, of an amber to chocolate 

 brown colour; hinge-teeth moderately strong; pseudocardinals 

 slightly ragged, three in the right valve, of which the middle is 

 the largest, and three in the left valve, of which the posteriormost 

 is the best developed; laterals slightly arched, single in the right 

 and two in the left valve ; anterior muscle scar deeply impressed , 

 posterior quite shallow ; nacre shining white in the umbonal region 

 but with a light bluish tinge below. 



The type-series was collected by Fea in the Houngdaran 

 River, Meetan, Tenasserim, Lower Burma. 



Parreyssia smaragdites (Benson). 



18O2. Unio smaragdites, Benson, Ann. Mag. Nat. Hist., (3) X, p. 190. 

 1866. Unio smaragdites, Blanford, Journ. As. Soc- Bengal XXXV, p. 



147- 



1876. Unio smaragdites, Hanley and I heobald, op. cit., p. 5, pi. x, fig. 



1877. Unio andersoniana (in part), Nevill, Journ. As. Soc. Bengal, 



XLV1. p. 40. 



1878. Unio andersoniana (in pari), Nevill, op. ci't., pp. 901, 902, pi. 



lxxx, figs. 9, 9a, 9/;. 



1889. Unio smaragdites, Tapparone-CanelYi. up. cit., p. 343. 



1890. Unio smaragdites, Paetcl, up. cit., p. 167. 



1899. Unio smaragdites, von Martens, op. cit., p. 39. 



1900. Parreysia smaragdites, Simpson, op. cit., p. 843. 



1914. Parreysia favidens (in part), Simpson, op. cit., pp. II09, 1110. 



1915. Parreysia (Parreysia) smaragdites, Preston, op. cit., p. 163. 



Simpson recently regarded P. smaragdites as only a synonym 

 of P. favidens, but the former species, as is clear from the large 

 series of specimens in the Indian Museum, is quite distinct from 

 the latter. Nevill's large series of Unio andersoniana from Burma 



