MAZATLAN BIVALVES 91 
ficiently perfect to describe with tolerable accuracy; and 
fragments of 5 others presenting characters by which they 
may be hereafter distinguished. 
124. Carpium (L&VICARDIUM) ELATUM, Sow. 
Pyro. Zool. Soc. 1833, p. 84.—Rve. Conch. Ic. sp. 41, pl. 8, f. 41. 
This most magnificent cockle is known at once by its large 
size, smooth surface and yellow colour. It has however very 
faint, nearly obsolete ribs, covering the body of the shell ; but 
even these are not to be seen ona large, distinctly marked, 
posterior and a smaller anterior portion. About the umbos 
there are no longitudinal ribs, but very faint concentric ridges 
of growth. The shell has a decided posterior gape: edges 
crenated within, except at the smooth parts: posterior lateral 
tooth in one valve marginal. Epidermis thin, crossed with 
numerous very fine concentric ridges. 
IfI have rightly affiliated the young shells, (but there is 
nothing intermediate between ‘11 and 2°63,) in its early state 
it is somewhat spotted, and much more transverse. The little 
shells suit better the description of C. Elenense. The teeth 
vary greatly in size, and the shells in thickness. Some of the 
young shells under a low power, and all under a high one, dis- 
play a pustulose surface, which Pmay be traced near the umbos 
of the smallest distinct specimen of C. elatum. The smallest 
minute valve is ‘03 across; the largest specimen measures 
long. 5°85, lat. 4°58, alt. 3°92. 
Hab.—Guaymas, in sandy mud at low water, Mus. Cuming.— 
San Diego, Lieut. Green.—Mazatlan ; not uncommon ; L’pool 
&§ Havre Col. 
Tablet 446 contains the smallest and largest distinct speci- 
mens.—447, 3 perfect and 2 imperfect valves of C.? elatum, jun. 
125. CaRDIUM PROCERUM, Sow. 
Proc. Zool. Soc. 1833, p. 838.—Mill. Syn. Test. Viv. p. 216.— 
Sow. Conch. Ill. no. 61, pl. 50, f. 23.—Rve. Conch. Syst. pl. 77, 
f. 23 :—Conch. Ic. pl. 10, £ 51.—Hanl. Deser. Cat. p. 140.— 
Menke, Zeit. f. Mal. 1847, p. 188, no. 51.—_B. M. Cat. D’ Orb. 
Moll. p. 74, no. 659.—C. B. Ad. Pan. Shells, p. 267, no. 433. 
This shell deserves favourable regard not only on account of 
the beauty of its form, but also because it has been quoted in 
