LAMELLIDE^S. 183 



well in other respects ; juvenile specimens are bright brownish- 

 green, older ones blackish ; the following are the measurements 

 of a series at various stages of growth : 



1. 2. 3. 4. 5. 6. 



Lat 124 92 79 72 65 43 mm. 



Long, (from urnbones) . . 49 40 36 32 28 19 mm. 

 Long, (from posterior ex- 

 tremity of wing) 56 46 39 37 32 21 mm. 



Diam 26 25 20 20 17 llmm. 



The wings average two-thirds of the length. The lower margin 

 in young specimens is fairly straight in the middle, in older ones 

 slightly curved inward. The edge running backwards from the 

 uinbones, separating the posterior from the lateral surface, is 

 always distinct. The hinge-teeth are nodulated, but comparatively 

 small. 



Hob. The Chindwin Eiver, near Kalewa; also in the River Tu, 

 one of the tributaries of the former. 



Young specimens of this variety, in outward form, greatly 

 resemble the U. marginalis var. anodontinus of the ' Conch. Ind.', 

 pi. 42, fig. 7. 



Subsp. corrianus (Lea). 



Unio corrianus, Lea, Philadelphia, Pa., Trans. Amer. Phil. Soc. v, 

 ser. 2, 1834, p. 65, pi. 9, fig. 25; Obs. Genus Unio, i, 1834, 

 p. 177, pi. 9, fig. 25; Hanley, Test. Moll. 1842, p. 207; Biv. 

 Shells, 1843, p. 207, pi. xx, fig. 60 ; Catlow & Reeve, Conch. 

 Norn. 1845, p. 57 ; H. & A. Adams, Gen. Rec. Moll, ii, 1857, 

 p. 491 ; Pastel, Conch. Sam. iii, 1890, p. 149. 



Margarita ( Unio) corrianus, Lea, Syn. 1836, p. 38 ; 1838, p. 25. 



Margaron ( Unio) corrianus, Lea, Syn. 1852, p. 38 ; 1870, p. 61. 



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

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



Original description : Shell narrow-elliptical, very transverse, 

 very inequilateral, subangular behind ; valves very thin ; beaks 

 scarcely prominent ; cardinal teeth thin and bladed ; lateral teeth 

 long, thin and nearly straight ; nacre pearly white and iridescent. 



Long. 25-5, lat. 53*5, diam. 13'5 mm. 



Hab. Calcutta. The following localities refer to specimens 

 in the Indian Museum : Seebsaugor (Peal) ; Pegu (W. T. Blan- 

 ford)', Balagunga, Central Sylhet; Madras; Berhampur, Mur- 

 shidabad District, Bengal (S. W. Kemp) ; Sambalpur ; Zayleymau, 

 Upper Burma (Dr. J. Anderson). 



Lea's description is amplified by the following notes : " Shell 

 narrow elliptical, very transverse, very inequilateral, subangular 

 behind ; dorsal line nearly straight ; substance of the shell very 

 thin ; beaks very slightly elevated and minutely waved at the tip ; 

 ligament long and slender ; epidermis smooth, dark brown ; rays 

 none ; cardinal teeth thin, bladed, single in the left valve and 



