MAZATLAN BIVALVES 95 



satis ; parte anteriore punctis ovalibus impressis decussatd ; 

 dentibus lateralibus approximatis. 



This charming little creature has a general resemblance to a 

 minute C. costatum ; but the large ventral costse are rather 

 rounded, with a little one on each side making them appear 

 somewhat trigonal. The anterior portion is strongly indented 

 with oval pits. The appearances it presents under the micros- 

 cope vary greatly according to the direction of the light. The 

 young shells have fewer ribs near the hinge, where the teeth 

 are not fully developed ; are rather less sequilateral ; and are 

 granulose on the ribs. Long. '12, lat. '11, alt. '08. 

 Hob. Mazatlan ; in Chama and Spondylus washings ; ex- 

 tremely rare. 

 Tablet 461 contains 2 valves, the largest and the smallest. 



134. CARDIUM O-RANIFEEUM, Brod. fy Sow. 



ZooL Journ. vol. iv. p. 367. Sow. Conch. HI. no. 38, pi. 49, 

 f. 17. Rve. Conch. Syst. pi. 76, f. 17 : Conch. Ic. pi. 8, 43. 

 Hani. Descr. Cat. p. 137. C. B. Ad. Pan. Shells, p. 266, 

 no. 430. .S. M. Cat. D'Orb. Moll. p. 73, no. 652. 

 The smallest valve found, which only measures '03 across, 

 scarcely shews a trace of teeth. The young shells are nearly 

 rectangular at the posterior end ; when older, they are obtuse 

 angled. The interstices between the ribs are decussated by a 

 series of rectangular impressed pits laid transversely. The 

 largest specimen found measures only long. '12, lat. '12, alt. *06. 

 Hob. Dug from a depth of about 6 inches in the mud of the 

 Estaro de Mazatlan ; Lieut. Belcher. Gulf of Mcoyia and 

 Xipixapi ; Cuming, _D' Orbigny. Panama, extremely rare, 

 C. B. Adams. Mazatlan ; a very few young valves and frag- 

 ments in the washings of Chamse and Spondyli ; L'pool Col. 

 Tablet 462 contains the largest (imperfect) valve, and two 

 small ones. 



135. ?CAEDIUM , sp. ind. (g.) 



? C. t. juniore suborbiculari, albidd, valde incequilaterali ; 

 margine dorsali postice recto, antice concavo ; costis- circiter xviii. 

 validis, rotundatis, approximatis, tuberculis latis armatis ; 

 dentibus elongatis, lateralibus distantibus. 



