100 TRANSACTIONS OF THE WAGNER FREE 



absolutely undistinguishable from the Carolina fossil* The largest 

 perfect specimen measures 4.2 inches in height, and nearly five inches in 

 greatest width. The form appears to be a rather variable one, the varia- 

 tion depending upon the relative convexity of the valves and ribs, the 

 latter, in the larger individuals, more generally assuming the flattened 

 form, with a submarginal carination ; the interspaces between the ribs 

 may also exhibit two or more faint carinations (imbricated longitudinal 

 lines), a character which was used by Conrad to distinguish P. Edgcco- 

 incnsis (Proc. Acad. Nat. Sciences, 1862, p. 291) from P. eborcns. I have 

 not seen any specimens of P. Edgccomcnsis, and am therefore unable to 

 say whether it corresponds to the variety of P. comparilis here indicated, 

 or not. 



Peoten (Pleuroneotes) Mortoni, Ravenel. 



Proc. Acad. Nat. Sci. Phila., ii, p. 96. 



Identified by one nearly perfect specimen and several fragments from 

 among the fossils of the upper Caloosahatchie. This species is most 

 intimately related to Pleuruncctes Japonicus, of the East Asiatic seas, 

 and can only be distinguished from it by the characters drawn from 

 the radiating raised lines of the interior of the shell, which in P. Mortoni 

 are disposed in narrow pairs, passing as such to the border. In P. 

 Japonicus the lines, while starting in pairs, lose their dual character long 

 before reaching the margin. 



Fecten nodosus, L. 



Syst. Nat., i2th ed., p. 1145. 



A solitary fragment, absolutely undistinguishable from the recent 

 species. 



Caloosahatchie, below Fort Thompson. 



Ostrea meridionalis, nov. sp. Fig. 35. 



Shell (at first) strongly plicated, suborbicular or elongated, becoming 

 massive and ponderous when full-grown, with an almost complete oblit- 

 eration of the plications ; the plications in the adult not visible on the 



I have examined what is supposed to be the type-specimen of Tuomey and Holmcs's 

 Pecten comparilis, and find that it differs somewhat from what has generally been assumed 

 to be species in question. The characters in which it varies, as the greater convexity of the 

 apical portion of the shell, and a slight reduction in the number of ribs, are, however, insig- 

 nificant, and inasmuch as the specimen is a solitary one, and consequently throws no light 

 upon individual variation, I think that the identity of the species with the form that Conrad 

 has recognized as P. comparilis, a shell attaining a very much larger size than that figured 

 and described by Tuomey and Holmes, may be fairly assumed. This form, moreover, is 

 that which was also subsequently identified with their own species by the South Carolina 

 geologists. Whether the species is distinct from Conrad's Pecten eboreus is a question 

 which, in the absence of a sufficiently large number of specimens for comparison, I am not 

 prepared to answer. 



