FROM PLIOCENE CLAY BEDS IN COSTA RICA. 355 



VOLUTA, Linn. 

 Y. MusiCA, Linn., S3^st. Nat., 12 Ed., p. 1194. 



There is an abundant fossil in the deposit corresponding with the recent shell 

 in all of its essential details, except in a persistently narrower mouth. But the 

 fossils differ among themselves in shape and strength of tuberculation, more than 

 they differ from the living shells. I have, therefore, retained the Linnsean name. 



MARGINELLA, Lam. 

 M. AVENA, Val., Kien., Sp. Gen. Coq. Yiv., Marginella, p. 17. 



A single specimen, agreeing perfectly with the figures and descriptions of this 

 species, as well as with recent examples with which I have compared it. Living 

 throughout the Caribbean province. 



M. CHRYSOMELiNA, Redf, Ann. N. T. Lye, iv. 492, t. 17, f. 2. 



Another unique specimen, kindly identified for me by Mr. Redfield. Living, 

 West Indies. 



M. MINOR, Adams (C. B), Ann. N. Y. Lye, v. 264. 



Also identified by Mr. Redfield by comparing with authentic specimens in that 

 gentleman's collection received from the author. Living, Pacific coast. 



M. ovuLiFORMis, Gabb, n. s., PI. 46, fig. 39. /-k^tw C^U^a^n^) ir yyi. ^c^llC J^eUi , i&k^f. 



Shell minute, robust; somewhat variable in form from that of a true Omla to 

 a "higher shouldered" variety, where the greatest width 'being hearer the upper 

 end, it approximates more nearly to the typical shape of the genus. This varia- 

 tion is very slight, however, and I have selected my most Ovula-Hke specimen for 

 illustration. In perfectly- adult specimens the spire is entirely hidden by the 

 heavy outer lip. Aperture curved ; outer lip crenulated, bearing three prominent 

 folds below the middle^ the columella ending in a fourth, stronger than the others, 

 which is continued around the anterior end of the mouth and merges into the 

 outer lip. Surface polished. 

 Length \\ mm. 



The hidden spire, the anterior notch nearly obsolete and bordered by a thick- 

 ened rim, and the general shape seems to ally this little shell to the subgenus 

 Volutella of Swain son. 



COLUMBELLA, Lam. 

 C. VARiA, Sby., Thes. Conch., t. 39, f. 116, 117. 



A common Panama species. My specimens are small, but not remarkably so, 

 and except that they are a very little more slender than the recent shells there are 

 no points of difference. 



