XXVII. ON THE GENERIC POSITION OF 

 SOME ASIATIC UNIONIDAE. 



By B. Prashad, D.Sc, Officiating Director of Fisheries, Bengal, 

 Bihar and Orissa, Calcutta. 



This paper deals with the anatomy^ etc, of Unionids from 

 countries as far apart as the Malay Archipelago and Burma on the 

 one hand and Palestine on the other. 



I. On the Genus Monodontina, Conrad. 



In a recent paper,* while describing the soft parts of an 

 Indian form of the genus Pseudodon, Gould, I questioned the pro- 

 priety of Simpson's grouping^ of the various species of that genus. 

 This observation was based on a study of the soft parts of the 

 species P. salvenianus, Gould — the type-species of the genus. I 

 felt myself justified in making the remark referred to, because my 

 description of P. salvenianus differed very materially from that 

 of the genus Pseudodon as compiled by Simpson {loc. cit.) from 

 Deshayes and Jullien's figure of P. moreleti} It was, however 

 impossible for me to go into the question in any greater detail as 

 I had no material of the other species. Through the courtes}^ of 

 Mr. Van der Doop of Sumatra, Dr. N, Annandale recently received 

 a large consignment of molluscs from Sumatra for identification, 

 and he very kindl}^ passed on the entire collection of Unionids 

 to me. This collection, though consisting of a single form, has 

 proved very valuable in enabling me to clear up a number of 

 doubtful points regarding the synonymy of some of the species ; 

 as also of the various groups assigned by Simpson to the genus 

 Pseudodon. According to that author, the species to which the 

 specimens must be assigned is P. chaperi (de Morgan). The ques- 

 tion of the validity of this species is, however, discussed at length 

 further on. 



To understand properlj^ the situation regarding the generic 

 name of the group to which the species under consideration 

 belongs, it is necessary to go into the history of the type-species of 

 Monodontina, namely M. vondemhuschiana (Lea). This species 

 was originally described by Lea as Margaritana vondemhuschiana * 

 though in a later work ^ he changed the name to Mar gar on [Mono- 



' Rec. Ind. Mus., XVI, pp. 289-297 (1919). 



2 Proc. U.S. Nat. Mus., XXII, pp. 501-1075 (1900). 



■^ Nouv. Arch, du Mus., X, pi. v, figs. 1-3 (1874). 



* Proc. Amer. Phil. Soc, I, p. 288 (1840). 6 |,ea, Synopsis, p. 45 (1852). 



