76 MAZATLAN BIVALVES 
often purple, especially on the hinge line. The smallest valve 
is ‘03 across; the largest measures long. 1°9, lat. 2°, alt. 1°28. 
Hab.—St. Elena, in coarse sand at low water, Cuming.— 
Keuador; St. Elena, D’ Orbigny.—S. W. Mexico, P. P. C.— 
Mazatlan; extremely common; L’pool & Havre Coll. 
Tablet 357 contains 7 young valves, [?], lunule not defined, 
very faint concentric lines of growth, anterior tooth elongated, 
as 1s usual in young Veneride. 
Tablet 358 contains 7 specimens of the normal chocolate 
colour.—359, 7 do. with white umbos.—360, 7 do. purplish 
tinge.—361, 7 do. light coloured, slightly spotted.—362, 7 do. 
with large patches of dark. 
108. Venus (? CoionE) ———,, sp. end. 
Tablet 363 contains 3 small valves, the smallest only ‘02 
across, smooth and white, which do not accord with any of the 
foregoing species. 
Hab—Mazatlan ; in shell washings: L’pool Col. 
Genus TAPES, Megerle. 
This genus, though the type of a sub-family of Gray, (Bb. MZ. 
Cat Ven., p. 159) approaches Venus (Chione, Megerle, Gray,) 
by insensible gradations. The following species may be ranked 
with either genus. The typical forms have not yet been found 
in this Zoological province. 
109. Tapes HIstRIonica, Brod. & Sow. 
Venus histrionica Proe. Zool. Soc. 1835, p. 41.—Hanl. Deser. 
Cat. p. 119;- Wood. Suppl. pl. 16, f. 31—B. M. Cat. D’ Orb. 
Moll. p. 67, no, 594.—Sow. Thes. Conch. p. 714, pl. 55, £. 52. 
Chione histrionica, Desh. B. M. Cat. Ven. p. 139, sp. 60. 
Tapes histrionica, Hanl. Col. suo. 
This belongs to a group of very closely allied species, of 
which T. granulata (B. M. Cat. Ven. p. 138,) is the W. Indian 
analogue, and T. straminea the Californian. It has the form 
and sculpture of a Tapes, with the teeth and pallial sinus of a 
Venus. The form varies in the greater or less development of 
the posterior angle, and in the flattening or rounding of the 
