LAMELLIDENS. 181 



Reeve, Conch. Icon, xvi, 1865, pi. 23, fig. Ill ; H. & T., C. I. 



1876, p. 19, pi. 41, fig. 1 ; Pastel, Conch. Sam. iii,1890, p. 157. 

 Margaron (Unio) layardii, Lea, 1870, p. 46. 

 Lamellidens lamellatus (Lea), Simpson, Washington, D.C., Smiths. 



Inst., Nat. Mus. Proc. xxii, 1900, p. 856. 



Original description : Shell subovate, transverse, somewhat 

 inflated, shining; valves very thin; beaks scarcely prominent, 

 undulated ; cardinal teeth long, thin and lamellar ; lateral teeth 

 long, thin, and nearly straight ; nacre bluish. 



Long. 38, lat. 64, diam. 25'5 mm. 



Hob. Bengal (Captain Lang}. This variety is represented by 

 specimens in the Indian Museum bearing the following localities : 

 Mandalay, Pegu, Bhamo (Dr. J. Anderson), also Calcutta and 

 Ceylon. 



Var. sublamellata, Preston, Eec. Ind. Mus., Calcutta, vii, 1912, 

 p. 305. 



Original description : An elongate, somewhat rostrate form, 

 having the hinge-teeth rather less developed. 

 Nab. Burma (W. Theobald). 

 The type is in the Indian Museum. 



Subsp. scutum (Sowerby). 



Unio scutum, Sowerby, Conch. Icon, xvi, 1868, pi. 94, fig. 510 ; 



H. & T., C. I. 1876, p. 22, pi. 46, fig. 1 ; Psetel, Conch. Sam. iii, 



1890, p. 167. 

 Lamellidens scutum (Sowerby), Simpson, Washington, D.C., Smiths. 



Inst., Nat. Mus. Proc. xxii, 1900, p. 857. 



Original description : Shell thick, unequally subventricose, 

 somewhat indented in the middle, somewhat depressed in front, 

 very inequilateral, oblong, obliquely sub-biangular behind, of a 

 uniform pitch-colour, smoothish ; ventral edge retuse, rising in 

 front : umbonal ridge elevated, the space behind it broad and 

 rather concave ; beaks but little projecting, nacre livid whitish ; 

 primary teeth slanting, lateral lamellae distant. 



The dimensions of the specimen figured in the ' Conch. Icon/, 

 and now 7 in the British Museum, are as follows : 



Long. 50, lat. 1 00, diam. 32-5 mm. ; 

 and those of a specimen in the Indian Museum collection : 



Long. 52-25, lat. 98, diam. 35'25 mm. 



Hab. Tenasserim (original locality); there are also specimens 

 labelled " Eangoon " in the Indian Museum. 



Var. humilior (von Martens), Arch. JSTaturg. Berlin, Ixv, pt. 1, 

 1899, pp. 45, 46, pi. 5, fig. 1. 



Somewhat more depressed than the typical form, but agreeing 



