t^^l

SPHiF.RTUM. 223
valde iiiflato ; latere postico magis prodiicto, subatteniiato, anguste
truneato.
Hah. Tenasserim.
The dimensions of a specimen in the British Museum are:—
Long. 14, lat. 17, diam. 11 mm.
A pale, uniform greenish-yellow shell ornamented with distant,
concentric riblets ; somewhat elongately ovate and considerably
inflated, especially remarkable for its thin texture.
Subfamily SPHiERIINiE.
Shell small, ovate or trigonal, lateral and cardinal teeth more
or less developed, ligament external; palUal line entire.
Distribution. World-wide.
Genus SPH^aiRIUM.
Sphcerium, Scopoli, ]777 ; Scopoli, Introdiict. p. 397.
Cfiama, d'Argenville, Hist. Nat. Lithol. Oonchyl. no. 9, 1742,
pp. 368, 374, pi. 31.
Tellina, Linnasus; Linn. Syst. Nat. 10th ed. i, 1758, p. C78.
Cardium, DaCosta, Brit. Conch. 1778, p. 173, pi. 13, tig. 2.
Ci/clas, Bruguiere, Encycl. M(5th. 1792, pi. 301.
JViu; Humphrey, Mus. Calonn. 1797, p. S9.
Muaouliam, Link, OoU. Univ. Bost., pt. S, 1807, p. \5l.
Cornea, Megerle, Mag. GeselL Naturf. Berlin, v, 1811, p. 50.
Corneocyclds, Ferussac, Diet. Sci. Nat. xii, 1818, p. 277.
Amesoda, itatineeque, Ann. G6n. Sci. Phys. et Nat. v, 1820, p. 310,
Ci/claditen, liriiger, Gesch. Urwelt. ii, 1823, p. 469.
Pisidimn, Verany, Lescris. Genova, ii, 1846.
TYPE, Splicerium corneum, Linn.; Europe.
Range. World-wide.
Shell thin, ovate, convex, subequilateral, covered with a fine
periostracum, smooth or concentrically striate; umboues lightl)'
anteriorly inclined ; anterior side rather shorter than the
posterior; margins of the valves simple; cardinal margins
thin; cardinal teeth small, that in the right valve often bilid,
fitting between two oblique teeth in the left; both anterior and
posterior lateral teeth compressed, divergent, somewhat projecting,
lamelliform double in the right valve, single in the left;
ligament external, weak, scarcely apparent; pallial line entire.
Animal having the edge of the mantle smooth ; foot tongue,
capable of considerable extension; siphons moderately long,
united at their base, separated at the end ; the branchial siphon
somewhat the longer and broader; siphonal orifices simple;
palpes triangalar, lanceolate; gills unequal, the outer the shorter
ami fringed.