FROM PLIOCENE CLAY BEDS IN COSTA RICA. 363 



BITTIUM, Leach. 

 B. MODESTUM, Orb. 46, fig. 56. 



Chemnitzia id., Orb., Moll. Cuba, I. 222, t. 16, figs. 22-24. 



B. DUBiUM, Orb. 46, fig. 5T. 



Chemnitzia id., Orb., Moll. Cuba, I. 226, t. IT, figs. 4-6. 



TRIFORIS, Desh. 

 T. TuRRis-THOM^, Chemn. sp. 



Turbo id., Chemn., Conch. Cab., t. XI, pp. 310, 213, No. 3022. 

 Cerithium id., d'Orb., La gagra, p. 155, PL 33, figs. 10-12. 



Comparatively common. Living in the West Indies. 



MODULUS, Gray. 



M. CATENULATUS, Kiist., Sp. 



Trochus id., K., Syst. Conch., p. 1 10, PI. 18, fig. 4. 

 Modulus id., H. & A. Ad., Gen. Rec. Moll. 



A single specimen. Species living, Pacific coast. 



RISSOA, Frem. 

 R. AuBERiANA, d'Orb., La Sagra, vol. 2, p. 22, PI. 11, figs. 34, 35. 



Three good characteristic specimens. Yet living; coast of Cuba. 



CAECUM, Flem. 



C. CRASSiQOSTTJM, Gabb, n. s., PI. 46, fig. 58. 



Shell curved, a little more abruptly at the apex than elsewhere ; ornamented 

 by large, round ribs, the interspaces being a very little narrower than the ribs. 

 In the interspaces are minute ridges placed in a longitudinal direction, as if they 

 were the rudiments of fine longitudinal ribs, which, however, do not rise over the 

 larger ones ; or they might be described as a series of regularly placed narrow 

 septa between deep pits ; since their presence produces an appearance of pitting 

 in the grooves, similar to that seen in some of the Actceons. The transverse ribs 

 are nearly of uniform size, except the last three or four, which are slightly larger 

 and placed more widely apart. 



Length 3 mm. 



C. ANNULATUM, Gabb, PI. 46, fig. 59. 



id., Gabb, Tr. Amer. Philos. Soc, vol. 15. 



A Dominican species, not yet found elsewhere ; figured here for purposes of 

 comparison. 



YERMETUS, Auct., Cuv. 

 Y. LUMBRiCALis, Linn., Mart., Conch. I, t. 3, f. 246. 



A few small fragments, but enough to identify the species with certainty. 



