286 MAZATLAN UNIVALVES 



adult state, should be so different in their early stage, is very 

 remarkable. A series of specimens from the inside of a West 

 African Pinna, of which the youngest is only '04 long, agree 

 exactly with the Mazatlan specimens now described. The 

 largest, 1*18 in length, would certainly have been called C. 

 squama if from Panama, though the epidermis is thinner than 

 in the ordinary Mazatlan specimens. They go through the same 

 changes of colour, deck margin, &c. as C. nivea ; and if they 

 had been born in an empty Cowry would prooably have deve- 

 loped into the genuine C. [unguiformis. As it is, they are 

 probably the C. G-oreensis,* a species which, according to 

 Dillwyn, has a tendency (like C. nivea) to develop foliations. 

 Whether the specimens quoted by Menke as C. Goreensis 

 belong to this species or to C. squama, cannot be told without an 

 examination of the vertex. Shells of exactly the same species, 

 some extremely young and well formed, others of the true C. 

 unguiformis shape, circular and elongated, were found in dead 

 East Indian Cowries from Singapore The species may abound 

 at Mazatlan ; but as almost all the vast numbers of shells sent 

 were perfectly fresh, there is no knowing what the dead ones 

 contained. The largest Mazatlan shell with the apex perfect 

 measures long. '12, lat. '08, alt. '02. Others, which have lost 

 the apex in growth, may belong either to this species or to 

 C. nivea. 



JIab. Mediterranean, Africa, Singapore, North and South 

 America, East and West ; fossil in tertiary strata ; v. supra. 

 Callao, Peru, very fine, in dead shells, B. M. Col. D'Orbigny, 

 not in Cat. Mazatlan ; extremely rare, in dead shells, &c. ; 

 L'pool Col. 



Tablet 1430 contains 3 sp. young. 1431, an adult sp. in 

 empty Trivia radians. 



GENUS CKFCIBULUM, ScJium. 



Crucibulum, ScJium. Ess. no. 8, 1817 : Gray, *Proc. Zool. Soc. 



1847, p. 157, no. 270 ~H. $ A. Ad. Gen. vol. i. p. 365. 

 Dispotsea, Say, Journ. Ac. N. S. Phil. vol. iv. 1124 

 Calypeopsis, Lesson, 1830, Brod. 1834. 



* The young of Cr. fornicata, as appears from specimens from Staten Island 

 m the collection of R. M' Andrew, Esq. is of the type Cr. Goreensis, Q-mel. but 

 with only one large tumid whirl (as in Crucibulum imbricatum,) lying imbedded 

 in the normal portion. Inside with first deck at an angle with the succeeding. 



