I.AMIvLLinENS 1 1 73 



laterals nearly or quite straight ; muscle scars shallow ; nacre 

 bluish, sometimes deep blue. 



Length JJ, height 45, diam. 23 mm. 



Length 70, height 36, diam. 25 mm. 



India; Ceylon. 

 Unio lamellatus Lka. Tr. Am. Phil. Soc, VL 1838, p. 19, pi. vi, 



fig. 16; O'bs., n, 1838, p. 19, pi. VI, fig. 16.— Hanley, Biv. 



Shells, 1843, P- 194' pl- XXI' fig- 49-— Chenu, 111. Conch., 



1858, pi. xxii, figs. 3, 30, ^b. — SowERBY, Conch. Icon., XVI, 



1866, pi. hu, fig. 272. — HanlEy and Thkobald, Conch. Ind., 



1876, p. 21, pi. xuv, fig. 7. 

 Margarita (Unio) lamellatus Lea, Syn., 1836, p. 26; 1838, 



p. 20. 

 Margaron (Unio) laiiicllatiis Lea, Syn., 1852, p. 29; 1870, 



p. 46. 

 Lamellidens lamellatus Simpson, Syn., 1900, p. 856. 

 Lamellidcns marginalis var. lamellatus Preston, Rec. Ind. 



Mus., VII, 1912, p. 304. 

 Unio layardii Lea, Pr. Ac. N. Sci. Phila., Ill, 1859, p. 153; Jl. 



Ac. N. Sci. Phila., I\', i860, p. 243, pi. xxxvi, fig. 122; Obs., 



VII, i860, p. 61, pi. XXXVI, fig. 122. — Reeve, Conch. Icon., 



XVI, 1856, pi. xxiiT, fig. III. — Hanley and Theobald, 



Conch. Ind., 1876, p. 19, pi. xli, fig. i. 

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



The shell is generally rather thin, the epidermis is almost 

 always smoky, and is occasionally bordered by a lighter band. 

 The type is not in the Lea collection. 



Lamellidens scutum (Sowerby). 



Shell elongated, rhomboid, subinflated, inequilateral, with 

 dorsal and basal lines straight and parallel ; dorsal slope ob- 

 liquely subtruncate; posterior ridge widely double, ending in 

 a wide biangulation below the median line ; beaks apparently 

 not much elevated ; surface smooth, of a uniform^ pitch color ; 

 teeth compressed ; pseudocardinals slanting ; laterals remote ; 

 nacre livid whitish. 



Length 100, height 50 mm. 



Tenasserim. 



