t^^l

LAMELLIDEXS. 183
well in other respects ; juvenile specimens are bright brownishgreen,
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 umbones) .. 49 40 36 32 28 19 mm.
Long, (from posterior extremity
of wing) 56 46 39 37 32 21 mm.
Diam 26 25 20 20 17 11 mm.
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
umbones, separating the posterior from the lateral surface, is
always distinct. The hinge-teeth are nodulated, but comparatively
small.
Hab. 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. lud.',
pi. 42, fig. 7.
Subsp. corrianus {Lea).
Unio corrianus, Lea, Philadelphia, Pa., Trans. Amer. Phil. Soc. v,
ser.-2, 1834, p. 05, pi. 9, fig. 25; Obs. Gemis Vnio, i, 1834,
p. 177, pi. 9, %. 25; Haiilev, Test. Moll. 1842, p. 207; Biv.
Shells, 1843, p. 207, pi. xx, iig. 60; Catlow & Reeve, Conch.
Nom. 1845, p. 57 ; II. & A.. Adams, Gen. Eec. Moll, ii, 1857,
p. 491; Pffitel, Conch. Sam. iii, 1890, p. 149.
Marjjarita ( Unio) corrianus, Lea, Syn. 1836, p. 38; 1838, p. 25.
Margaron {Unio) corrianus, Lea, Syu. 1852, p. 38; 1870, p. 6L
LameUidcns corrianus (Lea), Simpson, Washington, D.C., Smiths.
Inst., Nat. Mns. Proc. xxii, 1900, p. 857.
Oriffinal 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. Blanford);
Balagunga, Central Sylhet; Madras; Berhampur, Murshidabad
District, Bengal {S. W. Kemp) ; Sambalpur ; Zayleymau,
Upper Burma {I)r. 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