148 UNIONID.13. 



following measurements oE four specimens in the Indian Museum 

 show: — 



1. 2. 3. 4. 



Long 19 19 14 16-25 mm. 



Lat 33-5 31-25 22-5 23 mm. 



Diam 12 11-25 8-75 9-25 mm. 



Yai\ siliguriensis, Preston. 



Unio st'/i(/uriensis, Preston, Ilec. Ind. Mas., Calcutta, ii, p. 47 (fig. 

 in text) ; op. cit. vii, p. 293, as N. (Ii.) lima, var. siliguriensis. 



Original description : — Shell inequilateral, ovate oblong, reddish 

 brown, sculptured with concenti-ic lines of growth and oblique 

 transverse wrinkles, these latter being especially marked poste- 

 riorly ; anterior side rounded ; posterior side acuminately rounded ; 

 dorsal margin arched ; ventral margin very slightly contracted in 

 the middle ; umbones much eroded ; interior of shell iridescent, 

 pale bluish white. 



Long. 21, lat. 37-75 mm. 



ITab. Siliguri, N. Bengal. 



Type in Indian Museum, Calcutta. 



Genus PHYSUNIO. 



Phi/siinio, Simpson, Washiugton, D.C., Smiths. Inst., Nat. Mns. 

 Proc. x.xii, 1900, p. 830. 



Type, Unio (jravidus. Lea, from Siam, Cambodia, and Cochin 

 Cliina. 



Rancje. Siam; Cochin China ; Cambodia; Sumatra; Assam. 



Original description : — Shell thin, irregularly obovate, narrowed 

 in front, decidedly produced at post base, pointed behind, and 

 posteriorly winged, with a moderate posterior ridge and often a 

 second or third faint ridge above it ; beak sculpture zigzag radial, 

 somewhat disposed in two sets, the one down the posterior ridge 

 slightly nodulous ; posterior slope having ii'regular radial coi-ru- 

 gations, the rest of the shell smooth ; epidermis often cloth-like, 

 with one or more green rays on the posterior slope ; hinge-line 

 curved ; a single obliquely granularly striate pseudocardinal and 

 generally three laterals in the left valve, and two pseudocardinals 

 and two laterals in the right, all greatly compressed ; beak cavities 

 deep; muscle sears irregular; nacre bright, bluish, and iridescent. 



Animal unknown. 



Section LENS. 



Lens, Simpson, Washington, D.C., Smiths. Inst., Nat. Mus. Proc. 

 xxii, 1900, p. 831. 



Type, Unio eximnis, Lea, from Siam and Cambodia. 



