1 6 Bulletin ^-^ i6 



among the, rei)resentati\'e,s of the species just described, which 

 seem at first sight to belong to P. pouhoni. But upon direct 

 comparison of the two the left vah'e of poidsoni is never fiat and 

 in some instances decidedly gibbous, whereas in this species the 

 fragment .figured indicated a plane, or even concave valve. 

 Again, the ribs on the posterior ear are much more numerous in 

 this North Carolina species and the posterior cardinal angle less 

 than 90°. The tops of the ribs in pouhoni appear broad and 

 tri-partite ; in this species, bi-partite. The concentric sculptur- 

 ing is much the same in both species. However, a large series of 

 these forms may cause them to be finalh' regarded as one species. 

 If so, it would seem that a considerably greater geologic range 

 should be given to -this species than has been admitted heretofore 

 else the horizon on the Trent whence these specimens came is far 

 higher than has been suspected. A rather near relative oi poiil- 

 soni has been described b}' Dall as Biirnsii from the Chipola marls 

 of Florida. (Trans. Wag. Ill, 1898, p. 720, pi. 34, fig. 8.) 

 Conrad's <f//.ffl'/?^^^ from "near Santee Canal, South Carolina, in 

 white, friable limestone" is general!}' referred Xo poid son i Wort. 



Pecchiolia dalliana, n. sp., PL 2. Fig. 7. 



Specific cJiaracterization. — Size and general appearance as in- 

 dicated b}' the figure ; extremel}'^ inflated and general!}' Exogy- 

 roid surface marked by numerous radiating small ribs becomifig 

 stronger and farther apart as the position of the umbonal ridge 

 ia approached ; there occasional inter- riblets appear ; passing the 

 umbonal ridge the strength of the ribs decreases to the ligamental 

 margin ; a radiating channel divides the post-umbonal into two 

 nearly equal portions ; concentric markings consist of numerous 

 rather irregular and ill-defined undulations, strongest basally. 



This shell is strikingly similar to P. wevunelensis Vincent from 

 the ''Sables de WemmeV (Bull. Soc. royal Mai. de Belg. vol. 32, 

 1897, p. XXX ) and, since these sands are the equivalent of the 

 Barton Beds of England one instinctive!}' thinks of the aid, small 

 though it may be, that this form may render us in correlating 

 the upper Eocene deposits on either side of the Atlantic. 



