1866.] Contributions to Indian Malacology. 149 
No. 43.—Unio rxorzescens, Gould. Tavoy. 
Gould, Proc. Bost. Soc. Nat, Hist. I., 141. 
» Ot. Conch, p. 191. 
Apparently, from the description, another ally or variety of the U. 
marginals type. 
No. 44.—Unto generosus, Gould. Tavoy. 
Gould, Proc. Bost. Soc. Nat. Hist, II., 220. 
» Ot. Conch, 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.— Unto tutsus, Lea. Newville, Tavoy. 
Lea, Jowr. Acad. Nat. Sci. Phil, III., 302, pl. 27,17. 
I have not access to the description or figure of this species. 
No. 46.—Unio crispisutcatus, Bens. Bangong R. near Thayet 
Myo, Pegu. 
Benson, Ann. and Mag. Nat. Hist., 1862, 3rd Ser. 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. crispatus, 
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. Unto Puato, Bens. Ava and Pegu. 
Benson, Ann, and Mag. Nat. Hist., 1862, 3rd Ser. X., 198. 
A solitary valve was sent to Mr. Benson by Mr. Theobald, who gave 
the locality as Ava. Isubsequently 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 marginalis, 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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