1 6 Bulletin 33 16 



among the representatives of the species just described, which 

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

 comparison of the two the left valve of poulsqni is never flat 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 0 . The tops of the ribs in poulsoni 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 finally 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 of poul- 

 soni has been described by Dall as Burnsii from the Chipola marls 

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

 Conrad's elixatus from "near Santee Canal, South Carolina, in 

 white, friable limestone" is generally referred to poulsoni Mort. 



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



Specific characterization. — Size and general appearance as in- 

 dicated by the figure ; extremely inflated and generally Exogy- 

 roid surface marked by numerous radiating small ribs becoming 

 stronger and farther apart as the position of the umbonal ridge 

 is 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. wemmelensis 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 instinctively 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. 



