98 
Bulletin 35 
348 
Page 177 
% 4. Descriptions of sojie Species of Westindian 
Molluska. 
I take ad\’'antage of the present opportunity' to give sketches 
and descriptions of five shells, two of which have been pre- 
viously described, but not figured ; the other three are new. 
Of the five, four are inhabitants of the Gulf of Paria, and 
the fifth is a small but curious shell from the miocene of 
Jamaica. Mchila lintca and Periploma orbicularis were 
dredged in the Gulf of Paria by Mr. W. O. Crosby, of the 
Boston Society of Natural History'. Mr. Crosby' discovered 
not only the species mentioned in this communication as 
dredged by' him, but several others which he kindly' com- 
municated to me, and which are of remarkable interest as 
being either identical with, or nearly allied to fossils of the 
Westindian miocene. As the specimens referred to are all 
dead shells, dev'oid of colour, it has occurred to me as a 
possibility that they might have been derived from some 
tertiary bed at the bottom of the Gulf. An hypothesis like 
this, however, would be at once refuted by the finding of a 
single living example. 
I. Periploma orbicularis w. sp. (PI. vii., f. 13). 
Suborbicular, subequilateral, somewhat compres.sed, thin, 
nacreous internally', shagreened externally by minute rugo- 
sities disposed in radiating lines, and covered with a thin 
epidermis ; anterior side regularly rounded ; po.sterior side 
somewhat produced, sinuate, and obliquely' truncate; umbones 
prominent, fissured. Height 25 mill., length 30 mill. 
Resembles the Periploma compressa of D’Orbigny' (Voy. 
Amer. Merid., p. 514, pi. Ixxviii., f. 19, 20), but having a 
greater relative height from the umbo to the margin, is more 
