MAZATLAN UNIVALVES 325 



Hob. Mazatlan ; abundant on Spondylus, not uncommon on 



Chama, Modiola capax, &c., rare on Ostrea iridescens ; 



L'pool fy Havre Coll. ? Panama, 1 sp., C. B. Adams. 



Tablet 1531 contains 4 sp. smooth state. 1532, 11 do. partly 

 smooth, partly waved. 1533, 4 do. waved state adolescent. 

 1534, 7 do. adult. 1535, 2 sp. jun. and 2 adult, with opercula. 



Tablet 1536 contains 4 sp. deformed growth, and 1 pierced by 

 a tiny proboscidean. 1537, 1 sp. plug extremely prominent ; 1 

 do. with the profile line very slightly arcuated ; 1 do. deformed. 



Tablet 1538 contains 3 sp. probably belonging to this species, 

 but closely approaching C. Ia3ve. 



SECTION C. FAETULUM. 



C. t. l&vi, cyliiidraced, scepius utrinque contract A ; aperturd 

 sape declivi. 



This group is named from the general resemblance in form 

 to a little sausage. Some species however approach the long 

 tapering Elephantulum, while others are approached by the 



ringed Anellum. 







^ 372. C^CUM L^VE, C. B. Ad. (diagn. auct.) 



C. (Fartulum) t. junior e " C. undato" exacts simulante ; 

 t. adultd eidem simili, sed Icevi, nitidd, haud undatd, interdum 

 ante aperturam plus minusve tumidiore ; aperturd et apice 

 minus contractd ; operculo concavo, suturis minus distinctis 9 

 texturd semicorned, brunneo tinctd. 

 C. B. Ad. Pan. Shells, pp. 162, 311, no. 214. 



This shell, imperfectly described by Prof. Adams from two 

 specimens varying in age, is so remarkably like C. undatum 

 not only in its general habit but in several minute particulars, 

 and especially in the shape of the plug and mouth, that aber- 

 rant individuals of each are very difficult to distinguish. 1 

 know of no character by which the young shells can be separ- 

 ated. When it arrives at the "monstrosum" stage, the 

 absence of undulated rings in the bowl of the pipe becomes a 

 marked and uniform character. In the adult, the cylinder is 

 rather less contracted at the two ends, and the aperture a 

 trifle less slanting. Before the contraction of the aperture, 

 the tube is sometimes swollen, which has never been observed 

 Sept. 1856. & 



