must "be added to the li ^. .■'he oanto iJomin.p-iati form v/hich Gabb (1) 

 called 2« lavaleana d.'Orbigny (2) is very close, but is lars-er, 



(1). Traos . Am. Philos . See., nrvrsrr., vol. 15, p. '- 17, 1873. 

 (2^. loc. Git., p, 284, pi. 2 7, rifrs. 9-12, 1853. 



T?vlth the base more decidedly flered oosteriorlj, the posterior 

 raarsln straighter and with a steeper slope, the posterior slope 

 narrower and the sculpture slightly- coersfir. In penersl terms 

 the same is true for his Costa Riean Iilocene lavaleana (3); 

 while the Costa Pdcan Pliocene form under that narr.e (4) is even 



(3), Jour. Acad. Hat. Cci., Philadelt)hia, 2ncl ser., vol. 8, n. 

 343. 



(4). idem, p. 371. 



more elongated, "^he sin'~:le valTe from Gatim, ■> '^'^■- •'-i fied as 

 sericea is perhaps distinot, beins- larger, with astraipjiter pos- 

 terior margin, more acute poster o-ventral angle, s_ rr post- 

 erior £lo"oe . 



Qgcurrenee .- IJoper Olip-ocene: ?Gatun formation, Panama 

 (Pro7,Ti and Pilsbr;-, 1911); lov/er I'iocf^-T^: ^.n-.-ripn hrdn^ "'oTrde"., 

 Jamaica fDall, 1898). ? Pliocene ('): Trinidad i Gu -p^ , 1874). 



