XI. DESCRIPTION OF A NEW SPECIES OF 

 MARGARITANOPSIS (UNIONIDAE) FROM 

 THE SOUTHERN SHAN STATES, WITH 

 NOTES ON SOLENAI'a S L E N I F R M I S . 



By IvT.-Coiv. H. H. Godwin- Austen, F.R.S. 

 (With Plate XV.) 



Feddon and Theobald were the first to visit and collect 

 mollusca in the Shan country in 1864, but they did not penetrate 

 to the neighbourhood of the Inle Lake which is not^ as far as I 

 can remember, mentioned in their Geological Reports. It was not 

 until Colonel R. Woodthorpe, R.E., visited Fort Stedman in 1894 

 on his way to survey the Siam frontier that he obtained any shells 

 from this piece of water or its neighbourhood. Among them is 

 the remarkable large bivalve, which I have named after him, but 

 never as yet had an opportunity of publishing. The animal has 

 not yet been seen nor has that been described of its possible ally 

 Solenaia soleniformis, Bs. of Cachar.^ 



I append the description of Unto laosensis, to which the Shan 

 species comes nearest. 



Genus Margaritanopsis, Haas, 1912. 



Haas in Martini u. Chemnitz, Sysf. Conch. Cabinet, Bd. IX (ii) 2, pp. 



I2I-I22, pi. xii, figs. 1-2 (1912). Laos Mountains, Cambodia, Siam. 



Mons. Mouhot. Diam. 0-9, length r2, breadth 3 inches. 

 C. Torrey Simpson, Des. Cat. Naiades, p. 520 (1914)- 

 Sowerby, Conch. Icon., XVI, pi. xlvii. f. 256 (1866). 



Type, Unio laosensis, Lea. 



It is thus described. " Shell elongated, arcuate, rather solid, 

 not inflated, inequilateral; beaks slightly elevated, not full, thin 

 sculpture consisting of ridges that nearly follow the growth lines, 

 posterior ridge high. Very wide and rounded, anterior end of the 

 shell rounded, posterior end a little wider , rounded or feebly pointed, 

 surface with rude, concentric growth lines, epidermis brownish- 

 green, or greenish-brown and subshining in young shells, brown or 

 blackish and dull in old ones : left valve with two small stumpy 

 pseudocardinals, the anterior one often almost obsolete, and two re- 

 mote small laterals; right-valve with two peseudocardinals, the 



' Since this was written a description of the animal of S. soleniformis has 

 been published by Dr. Ekendranath Ghosh in Rec. Ind.Mus. XV, pp. 109-122, 

 pi. xvi (19 1 8). — A''. A. 



