MAZATLAN UNIVALVES 345 



Comp. C. sacrata, Gould, Exp. Shells, p. 60 : ( = C. California, 

 Nutt. ms. Var. = C. fuscata, Gould ms. teste Nutt.) Sab. 

 Upper California. 



Comp. Cerithium (Potamides) Hegewischii, Phil, in Zeit. f. 

 Mai 1848, p. 19, no. 81. (Sab Mexico, Pubi.) 



Desh. & C. B. Ad. both doubt the identity of Sow.'s and 

 J&en.'s species. The Mazatlan shells scarcely accord with 

 either, and may prove distinct. The genus is not yet well 

 understood. Sow. unites to this Phil.'s species, which is pro- 

 bably an allied form from the West Indies ; also C. iostoma, 

 Pfr. (Pubi) ; also C. helicoide, "the narrow variety without 

 varices," C. IB. Ad. (Pubi) ; as well as (rightly) C. yalidum, 

 C. B. Ad. "Shells of Jamaica."* 



The Mazatlan species scarcely agrees with the S. American 

 shells in D'Orbigny's collection ; and have much more the 

 appearance of the variable Calif ornian species, C. sacrata, 

 which however has much fainter spiral and stronger transverse 

 sculpture. It most closely resembles a W. Indian species, 

 which is probably that intended by Philippi, but differs in its 

 uniform dark colour. The scarcely varicose forms are known 

 at once from the dwarf variety of C. Montagnei by the strong 

 spiral sculpture, even on the upper whirls, the subquadrate 

 aperture, and the absence of thick labial deposit. The surface 

 is scarcely corrugate ; epidermis rather thick, rough and 

 deciduous. The operculum closely resembles that of C. Moii- 

 tagnei, but is slightly less concave, and somewhat larger in 

 proportion. Occasionally cup-shaped bodies are found on it, 

 which look like the remains of egg- cases. It generally measures 

 about "95 by '35 ; an extraordinarily large one measures 

 long. 1*36, long. spir. 1*04, lout, (sine var.) '46, div. 20. 



Tablet 1628 contains 5 sp. in various stages of growth. 1629, 

 3 do. intervarical state. 1630, 4, do. solid, light mouth. 1631, 

 3 do. form more elevated. 1632, 5 normal state. 1633, 5 do. 

 varices strongly developed. 1634, 3 do. varices scarcely deve- 

 loped. 1635, 2 sp. varying in sculpture. 1636, 2 do. mended 

 after fracture. 1637, 1 sp. with operculum in situ ; and 3 

 separate opercula, one of which is scarcely spiral (? through 

 accident). 



* The inaccuracy with which the labours of Prof. Adams are quoted or ignored 

 by Mr. Sowerby, jun. may be co-ordinate with the execution of the remainder of 

 the Monograph, but scarcely does justice to the honoured name which the author- 

 inherits. 



