MAZATLAN BIVALVES 91 



fieiently perfect to describe with tolerable accuracy ; and 

 fragments of 5 others presenting characters by which they 

 may be hereafter distinguished. 



134. CaEDITTM (LiEVICAEDITJM) ELATUM, SoiC. 



Pro. Zool. Soc. 1833, p. SL—Eve. Conch. Ic. sp. 41, pi. 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 on a 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. 



If I have rightly affiliated the young shells, (but there is 

 nothing intermediate between ■lland2'63,) in its earlj' 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 sheUs in thickness. Some of the 

 young shells under a low power, and aU under a high one, dis- 

 l)lay a pustidose surface, which ?may 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.4i' 58, cdf. 3' 92. 



Sab. — Guaj-mas, in sandy mud at low water, Mus. Cimiing. — 

 San Diego, Lieut. G-reeii. — Mazatlan ; not imcommon ; L'pool 

 Sf Havre Col. 



Tablet 446 contains the smallest and largest distinct speci- 

 mens. — 447, 3 perfect and 2 imperfect valves of C. ? elatum, jun. 



125. Caedixjm peoceeum. Sow. 



Troc. Zool. Soc. 1833, p. 8?,.— Mull. Si/n. Test. Viv. p. 216.— 

 Sow. Conch. HI. no. 61, pi. 50, f. m.—Rve. Conch. Syst. pi. 77, 

 f. 23 -.—Conch. Ic. pi. 10, f. 5\.—Hanl. Descr. Cat. p. 140.— 

 Meyike, Zeit.f. Mai. 18^17, p. 188, no. 5\.—B. M. Cat. HOrh. 

 Moll. p. 74, no. 659.— C. B. Ad. Pan. Shells, p. 267, no. 433. 



This sheU deserves favourable regard not only on account of 

 the beauty of its form, but also because it has been quoted ia 



