148 Contributions to Indian Malacology. [No. 2, 



No. 39. — Unio Thwaitesii, Lea. Ceylon. 



Lea, Jour. Acad. Nat. Sci. Phil. 2nd Ser. IV., 246, pi. 37, f. 125. 



This shell only differs from the last in having a rather straighter 

 hinge line, and being slightly more inequilateral. If such differences 

 are to rank as specific, half a dozen " species" might be manufac- 

 tured out of any tank in Calcutta. The separation of these two forms 

 is perfectly unjustifiable in a genus like Unio. 



The above are the only species that I can trace specially described 

 from Ceylon. Lamarck's variety b. of Unio marginalis described as 

 var. testa minore, breviore, and 75 millimetres broad was also from 

 Ceylon (Lam. VI. 79). Sir Emerson Tennent, in his work on Ceylon, 

 enumerates only U. corrugatus besides U. marginalis. He, however, 

 adds that Mr. Cuming possessed six species from the island, which 

 had been sent to Mr. Lea. U. Thwaitesii and U. Layardi are doubt- 

 less two of these, as they were from Mr. Cuming's cabinet, but no 

 mention is made of the others by Mr. Lea. 



IV. — Burma. 



No. 40. — Unio Tavoyensis, Gould. Tavoy. 



Gould, Proc. Bost. Soc. Nat. Hist. I., 140. 



„ Ot. Conch, p. 190. 

 Kiister, Mart, and Chem., p. 166, pi. 48, f. 2. 



'* Closely allied to U. corrugata, Lam. which is less rounded and 

 less corrugated" (Gould, 1. c.) More nearly allied to Lamarck's than 

 to Chemnitz's type of U. corrugatus. Kiister's figure agrees well with 

 Gould's description, but represents a young shell, not mature. The 

 specimen figured was from the collection of Dr. Sturm (and not from 

 that of Dr. v. d. Busch). 



No. 41. — Unio crispatus, Gould. Tavoy. 



U. crispata, Gould, Proc. Bost. Soc. Nat. Hist. I„ 141. 

 „ Ot. Conch, p. 191. 



No. 42. — Unio foliaceus, Gould. Tavoy. 

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

 „ Ot. Conch, p. 191. 



An ally (variety ?) of U. marginalis, Lam. <c Closely allied to U, 

 Bengahnsis and Corrianus } Lea." (Gould, 1. c.) 



