FROM PLIOCENE CLAY BEDS IN COSTA RICA. 357 



Mr. Guppy's form than to the original described by Sowerby. This character 

 approaches then to C. striata^ Lam., which only differs from the present form in 

 being a little higher in the spire and still a little more strongly striated. 



We have in this group a beautiful illustration of development. The oldest 

 known forms of the shell, those of the Santo Domingo Miocene, are polished in the 

 adult state; the spire is always striated, and the markings when they exist on the 

 body whorl are so nearly obsolete as not to interfere with the generally polished 

 surface. The varices, three in number, are well marked on the adult. The outer 

 lip is usually expanded posteriorly and laterally so as to cause a false appearance 

 of a low spire ; and the markings on the inner lip are somewhat obsolete. In the 

 same formation in Jamaica the shell occurs, here retaining the juvenile character 

 of the striated surface over the body whorl, depriving it of its polished appear- 

 ance; and with this tendency to a sculptured surface, there is a nearly total disap- 

 pearance of the varices and an increase also of the size of the corrugation on the 

 inner lip. Still further west, and at a later period, we find the shell, yet abundant, 

 becoming more slender and especially diminishing the posterior expansion of the 

 outer lip, and with the sculpture character further developed. And finally, the 

 recent C. striata^ no doubt the lineal descendant of the above, is yet more slender, 

 the outer lip more sloping posteriorly, the spire only a trifle higher, and the sur- 

 face markings but a little more intensified! Keeve says he can obtain no infor- 

 mation as to the locality of the recent shell. The specimens in the museum of 

 the Philadelphia Academy are also without a locality label, but no doubt, from 

 the foregoing, the species will prove to be either from the Caribbean or the Panama 



province. 



MORIJM, Bolt. 



M. ONiscus, Linu., Sp., H. and A. Ad., Gen., v. 1, p. 219. 



Not common. 1 found but a single specimen. 



NATICA, Linn. 

 N. CANRENA, Linn., Mus., p. 674. 



Abundant. 



MAMILLA, Sebum. 



M. MAMiLLARis, Lam., Sp., A. S. V., v. 8, p. 628. 



Abundant. 



SCALARIA, Lam. 

 S. Candeana, d'Orb., La Sagra, vol. 2, p. 20, PL 11, figs. 28-30. 



A shell recent on the coast of Cuba, now found fossil for the first time, in the 

 clay beds of the Limon peninsula. . . 



