191S.] i\. Annandale: Molliisc-'i of the Inle Lake. 139 



Physunio micropteroides, sp. nov. 



Plate xix, figs. 1-3. 



Shell inequilateral, suboval, elongate, thin, with a broad low blunt 

 wing on the dorsal margin, rounded anteriorly, subtruncate and often 

 a little produced posteriorly, with a pair of low diverging ridges 

 (obsolete in old shells) proceeding backwards and downwards from 

 the umbo, with coarse irregular transverse striae on the surface, slightly 

 inflated ; the umbo rounded, not at all prominent ; epidermis dark 

 brown, with obscure concentric transverse dark or black lines ; nacre 

 rather dull, of a livid bluish tint ; lateral tooth long, thin, nearly 

 straight, on right valve trifid almost from its point of origin, on left 

 valve simple, its hinge-margin obscurely corrugated ; pseudo-cardinal 

 teeth on both the valves very short, curved, prominent, rounded 

 ventrally, the left tooth with the edge produced triangularly and some- 

 what retro verted ; edge smooth on both teeth. 



Measurements of shells {in millimetres). 



Type. 



Length of shell ... ... ... 58 55 55 



Greatest depth of shell ... ... ... 37 36 37 



Thickness of shell ... ... ... 15 16 15 



Type-sjjecimen. M. 11048/2, Zoological Survey of India {Ind. Mus.). 



Habitat. — Sluggish streams on the Yawnghwe plain, in dense mud 

 in about 3 feet of water. 



This species is very closely allied to Physunio micropterus (Morelet), 

 with shells of which from Cambodia I have compared my specimens. 

 It differs, however, in the form of the hinge, in its even less produced 

 wing, in its less prominent umbo and darker colouration. 



I hope that Dr. Ekendranath Ghosh will shortly publish a general 

 account of the anatomy of this and the succeeding species. ^ Mr. Baini 

 Prashad has given me a paper for this volume on the glochidia and 

 marsupium of both. 



The glochidium is parasitic on the fins of the small loaches Nemachilus 

 brevis, Boulenger and N. hrunneanus, mihi. 



Physunio ferrugineus, sp. nov. 

 Plate xix, figs. 4-9. 



This species is allied to the last one, but larger, with a thinner shell, 

 with the wing better developed, with the diverging longitudinal ridges 

 stronger, with the striae on the external surface finer and more reoular, 

 with the epidermis of a rich iron-brown (sometimes with darker con- 

 centric lines), with the nacre paler, \\'\t\x the lateral teeth more pro- 

 minent and the pseudo-cardinal teeth of a different shape (see figures). 

 In general appearance the young shell resembles P. semialatus.^ 



1 In Rec. Ind. Mus., XV (1918). The paper is now in piess. 



- Deshayes and Jullien, Nouvellea Archives dii Musevtn, X, p. 123, pi. vi, fig. 1, 2, 

 Bulldin, 1874. 



