igiQ-] B. Prashad : Asiatic Unionidae. 407 



4. The foot in the genus Monodontina is a much better de- 

 veloped structure than in Pseudodon. 



Relationships. — Frierson ^ in discussing the relationship of 

 Pseudodon resuspinatus, von Martens, says that the outline and 

 sculpture are ver}^ like that of the genus Virgus, while specimens 

 of Nodularia (probably brandtii from Japan) show a very close 

 kinship to Pseudodon in the teeth and general facies. I do not, 

 however, think that the comparison is quite correct for the sculp- 

 ture of Virgus (vide Simpson, loc. cit., p. 852) is quite different 

 from that of any of the species of Pseudodon that I have seen, and 

 also from that of the species that I now assign to the genus 

 Monodontina. The hinge also is quite different in the two genera. 

 The above remarks apply with equal force to the comparison made 

 by the same author between Nodularia (probably brandtii) and 

 Pseudodon, for the hinge and teeth in the group of Nodularia 

 japanensis, to which A^. brandtii belongs, are very different from 

 those of Pseudodon and Monodontina. Monodontina, on the other 

 hand, seems to have a rather close relationship with the group of 

 Nodularia contradens , which Haas {loc. cit., p. 173) has recently 

 separated into a distinct genus Contradens. 



Monodontina vondembuschiana (Lea). 



igoo. Pseudodon vondembuschiana, Simpson, op. cit., p. 836. 



1910. Pseudodon vondembuschiana, Haas, op. cit., pi. xliv, figs. 4, 5. 



A number of specimens of the t3^pical form are present in 

 the collection of the Zoological Survey, from Sarawak, and one speci- 

 men from the Philippine Islands (presented by the late Mr. W. Theo- 

 bald). Mr. H. B. Preston also identified some shells (No. M^-'V'-i) from 

 Pegu as P. vondembuschiana, although he does not mention this 

 species in his volume in the ' Fauna of British India.' These last- 

 mentioned specimens, however, do not even belong to the genus 

 Monodontina; they are rather specimens of Pseudodon crebristriatus 

 and P. peguensis. 



Var. chapcri (de Morgan). 



1885. Pseudodons cliaperi, de Morgan, Bull. Soc. Zool. France, X, 



p. 423, pi. ix, fig. I. 

 1900. Pseudodon chaperi, Simpson, Proc. U.S. Nat. Mus., XXII, p. 838. 



Both de Morgan and Simpson considered this a distinct spe- 

 cies. The large number of specimens of different ages received 

 from Sumatra, however, show beyond doubt that it is no more 

 than a variety of M. vondembuschiana. P. zollingeri, var. angu- 

 losa of Mousson {loc. cit.) also seems to me to be no more than a 

 variety of that species. Indeed, it is probably identical with the 

 var. chaperi, but it is impossible to express a definite opinion on 

 this point without further material. 



The record of the occurrence of this variety in Sumatra 

 greatly extends its range, for it was previously known from 



1 Nautilus, XXIV, p. 97 (191 1). 



