- 146 - 



Youn<=r iri'^ ivi r!n als , It sides "being more auriculate, have a greater 

 difference in altitude "between the posterior and anterior ends, 

 i. e., the ventral niar?rin ascends core rapidly anteriorly^ and the 

 ■am"bonal sulcation often persists to the ventral margin, thus pro- 

 ducing an almost bilobed appearance. Considerable difficulty was 

 experience'^- in distinguishing "between the young of ap:nastha and 

 wordeni, those belonging to agnastha are usually more elongate, 

 more auriculate and have more numerous and finer ribs. The adults 

 are readily separable, since the shell of v;ordeni is heavier, 

 larger, higher, more inflated and its ribs are coarser and high- 

 er. ?rora the anricule te perphaina , a^nastha differs by being small- 

 er, thinner, more elor^ate, less inflated and by having more nujn- 

 erous and finer ribs. A, acompoa Pall (1), of the ^hipola fauna. 



(1). Trans, '-^agner Free Inst. 3 1., Philadelphia, vol. 3, pt, 

 4, p. 64S, pi. 33, fig. 15, 1898. 



is more produced anteriorly, has a straighter base, vidder ribs 

 and the anterior ribs are divided. 



Occurrence .- lower Miocene: Bowden beds, Bowden, Jamaica. 



