er water species in the G-ulf and iintill ean waters and also, re- 



(1). Bull. Hus. Compt. Sool., Harvard, vol. 12, pp. 211-212, 

 pi. 4, fig. 3; pi. 5, fig. 12, 1886. 



ported from the Pliocene of the Tsthmns of Tehuantepec (2). 



i^he recent form is larger, more orbicular, '.vith larger auricles, 



less conspicuous external sculptnre, the internal lirae not quite 



(2). B8se, E., Bol. Inst. geol. Ile-ico, no. ^2 , pp. 52-55, 1906. 



as heavy, le.^s swollen and pointed at their distal end, and extend- 

 ing further toward the uraho. 



Oeciirrer:c e.- lov/er i-.Iioc ene : Bowden heds^ Bo-den, Jamaica. 



