t^^l

LAIIELMDBNS. 181
Eeeve, Conch. Icon, xvi, 1865, pi. 23, fig. Ill; H. & T.,'c. I.
1876, p. 19, pi. 41, tig. 1; PiBtel, Conch. Sam. 111,1890, p. 157.
Margaron {Unio) layardii, Lea, 1870, p. 46.
Lainellidens laniellatus (Lea), Simpson, Washington, D.C., Smiths.
Inst., Nat. Mus. Proc. xxli, 1900, p. 856.
Original description :—Shell subovate, transverse, somewhat
inflated, shining; valves very tliin; beaks scarcely prominent,
undulated; cardinal teeth long, thin and lamellar; lateral teeth
long, thin, and nearly straight; nacre bluish.
Long. 38, lat. 64, diam. 2o'5 mm.
Hah. Bengal {Captain Lang). This variety is represented by
specimens in the Indian Museum bearing the following localities :—
Mandalay, Pegu, Bhamo {Br. 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.
Hah. Burma ( W. Theobald).
The type is in the Indian Museum.
Subsp. scutum {Sowerhy).
Unio scutum, Sowerby, Conch. Icon, xvi, 1868, pi. 94, fig. 510;
H. & T., C. I. 1876, p. 22, pi. 46, fig. 1; Ptetel, Conch. Sam. ill,
1890, p. 167.
La7neUidens scutum (Sovtevhy), Simpson, Washington, B.C., Smiths.
Inst., Nat. Mus. Proc. xxii, 1900, p. 857.
Origincd 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 lamellse distant.
The dimensions of the specimen figured in the ' Conch. Icon.',
and now in the British Museum, are as follows :—
Long. 50, lat. 100, 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. Naturg. Berlin, Ixv, pt. 1,
1899, pp. 45, 46, pi. 5, fig. 1.
Somevsrhat more depressed than the typical form, but agreeing