1866.] Contributions to Indian Malacology, 149 



So. 43. — Unio exolescens, Gould. Tavoy. 



Gould, Proc. Bost. Soc. Nat. Hist. I., 141. 

 „. Ot. Couch, p. 191. 



Apparently, from the description, another ally or variety of the U. 

 marginalia type. 



No. 44. — Unio generosus, Gould. Tavoy. 



Gould, Proc. Bost. Soc. Nat. Hist. II., 220. 

 „ Ot. Couch, p. 201. 



I believe I possess this species. Specimens were sent to me by Mr. 

 Theobald from Pegu, which agree with the description fairly, except 

 that they are smaller than the type. 



No. 45. — Unio luteus, Lea. Newville, Tavoy. 



Lea, Jour. Acad. Nat. Sci. Phil. III., 302, pi. 27, 17. 



I have not access to the description or figure of this species. 



No. 46. — Unio crispisulcatus, Bens. Bangong R. near Thayet 

 Myo, Pegu. 



Benson, Ann. and Mag. Nat. Hist., 1862, 3rd Scr. X., 193. 



I am indebted to Mr. Theobald for specimens of this shell. It ap- 

 pears doubtful whether it be more than a variety of U. erispatus, 

 Gould, to which Mr. Benson does not refer in his description, and 

 with which he was possibly unacquainted. Gould's description is very 

 : brief, and gives the idea of a more coarsely sculptured shell ( " rugis 

 angulatis radiantibus undique crispata"} besides being somewhat 

 shorter ("from the dorsal to the ventral margin) in proportion to its 

 breadth, but these are not necessarily specific distinctions. 



No. 47. — Unio Pugio, Bens. Ava and Pegu. 



Benson, Ann. and Mag. Nat. Hist., 1862, 3rd Ser. X., 193. 



A solitary valve was sent to Mr. Benson by Mr. Theobald, who gave 

 the locality as Ava. I eubsequently found the same form in the Mya- 

 noung district of Pegu, and Mr. Theobald has since obtained larger 

 varieties, I believe from Prome. It is a well marked type, extremely 

 inequilateral, and with a peculiar acuminate form posteriorly. 



As already observed, the type form of Unio margincdis, Lam. 

 abounds in Pegu. I found unusually fine specimens in large swamps 

 about Henzada and Myanoung in the Irawady valley. The type gra- 

 dually passes by insensible gradations into a much less transverse 



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