4o8 Records of the Indian Museum. [Vol. XVI, 



Cambodia and Siam only. It probably occurs also in the Malay 

 Peninsula, the freshwater molluscs of which are little known. 



Var. inoscularis (Gould). 



1844. Anodoii inoscularis, Gou\d, Pi'oc. Boston Nat. Hist. Soc, I, p. 160. 

 1900. Pseiidodoii inoscularis, Simpson, Proc. C/.S. Nat. Mas., XXII, 

 P- 837- 



There are two specimens of this form in the collection, one 

 labelled " Tenasserim" and another " Tenasserim river." 



It differs from the typical form in the shell being much 

 smaller and more depressed, the posterior wing rather broader, the 

 surface smoother and the cardinal tooth better developed. 



Monodontina cumingii (Lea). 



1850. Aiiodonta cumingii, Lea, Proc. Zool. Soc. London, p. 199. 

 1900. Pseudodon cumingii, Simpson, op. cit., XXII, p. 837. 



A single specimen from Cambodia in the collection belongs to 

 this species. 



A point worth noting about M. cumingii is that the origin of 

 the cardinal tooth is exactly in line with the upper margin of the 

 shell. 



II. Sub- GENERA OF UN 10 FROM THE NEAR EasT. 



The specimens on which this part of the paper is based were 

 collected by Dr. Annandale in 1912 in the Lake of Tiberias.' The 

 entire collection of molluscs from this area was reported on by 

 Preston,^ but nothing was said by him about the anatomy of the 

 various forms ; further, the identifications of the two forms treated 

 of in this paper are not correct in view of later work. One of the 

 species belongs to Germain's recently proposed subgenus Rhom- 

 bunio,^ while I have found it necessary to give a new subgeneric 

 name to the other species. Annandale * also has pointed out the 

 great confusion that exists regarding the nomenclature of the vari- 

 ous species of the genus Unio from Palestine, but I am unable to 

 go into the question further owing to insufficient material of the 

 related forms. I have, however, adopted Germain's plan of divid- 

 ing the genus Unio into subgenera instead of groups as Simpson ^ 

 had done, because Germain's idea conduces to a clearer under- 

 standing of the relationships. 



Rhombunio, Germain. 



Germain proposed this subgenus in 1911 (/oc. cit.) for a group 

 superficially resembling that of Unio littoralis group. According 



' For further details about locality, etc., reference maybe made to Joiirn. As. 

 Soc. Bengal, IX, p. 17 onwards (1913). 

 2 Ibid., pp. 46=5-476, pi. xxvii (1913). 

 s Bull. Mus. b'Hist. Nat. Pans, XVII, p. 67 (191 1). 

 * Journ. As. Soc. Bengal, XI, p. 459 (1915). 

 ' Proc. U.S. Nat. Mus. XXII, p. 679 onwards (1900). 



