FROM PLIOCENE CLAY BEDS IN COSTA RICA. 369 



merges into the lip in front. Umbilical region covered with an unusually thin 

 layer of enamel. 



Diameter barely 1 mm. 



From the Dominican species it can be distinguished by its constantly smaller 

 size, flatter shape, and in the fact that the umbilical callus and adjoining inner lip 

 are much lighter and thinner. 



FISSURELLA,Brug. 

 F. NODOSA, Born. Mus. 426. 



Two good specimens. Living in the West Indies. 



LUCAPINA, Gray. 

 L. ALTERNATA, Say, sp., Joum. Phil. Acad., 1 ser., v. 2, p. 224. 



Fossil in the Miocene of Santo Domingo. Living in the West Indies and on 

 the Atlantic coast of the United States. 



DENTALIUM, Linn. 

 ■D. DENTALE, Linn. (?) Born. Mus. t. 18, fig. 13. 



I refer two fragmentary specimens to the Linnaean species with some doubt, 

 but with such imperfect material cannot be more certain. They agree in size and 

 amount of curvature with Sowerby's figure in Thes. Conch., but are not only not 

 twelve costate, but differ between themselves in this variable and unreliable 

 character. The largest has about thirty ribs, which show a marked tendency to 

 alternation in size, every other one being larger, thus reducing the larger ribs to 

 an approximation to the required number. The smaller specimen is much more 

 finely sculptured, and the ribs are markedly uniform in size. 



CYLICHNA, Loven. 

 C. SULCATA, d'Orb. sp. 



Bulla id., d'Orb., La Sagra, v. 1, p. 129, PI. 4 bis, f. 9-12. 



Cylichna id., Gabb, St. Domingo Memoir, Tr. Am. Phil. Soc, v. 15. 



Fossil in Santo Domingo, living on the Cuban coast, and now fossil in Costd 

 Rica. 



TORNATINi, A. Ad. 

 T. RECTA, d'Orb. sp. 



Bulla recta, d'Orb, La Sagra, PL 4 bis, figs. 17-20. 

 Tornatina id., Gabb, Mem. Tr. A. P. S., v. 15, 



The same remarks apply here as to the Cylichna. In the above quoted 

 memoir, among hundreds of typographical errors, the printers made this genus 

 Tornatina. The paper was printed during my absence in Costa Rica. 



75 



