1819.] NATURAL SCIENCES OP PHILADELPHIA. 225 



atlas, pi. 11 (20) fig. 8) to North Italy (Bellardi " Monog. Pleurot. 

 Foss. del Piem.," Memorie delict Reale Accademia di Torino, 2d 

 ser., vol. ix., p. 576). This species corresponds probably to some 

 extent with Sowerby's P. comma. Unquestionable specimens of 

 P. denticula from the Eocene of Alabama are to be found in the 

 American Museum of Natural History of New York. 



Mesostoma rugosa, nob. Proc A. N. S., Oct. 1879. 



This species might readily be mistaken for the M. grata, Desh., 

 of the Paris basin, from which it differs only in the greater num- 

 ber of its revolving ridges. 



Melania Claibornensis, nob. Proc. A. N. S., Oct. 1879. 



This diminutive Melania, which to my knowledge constitutes 

 the only essentially fresh-water gasteropod found to the present 

 time in the Claiborne marine formation, cannot in its characters 

 be readily distinguished from the M. mixta, Desh., of the Paris 

 basin (description and fig. in Desh. u Animaux s. vert."). Having 

 observed but one specimen, and not wishing to definitely deduce 

 its affinities from the characters drawn from a single example, I 

 have provisionally applied to the American shell the specific name 

 which it bears above. 



A close comparison of the Eocene mollusea of the east and west 

 Atlantic shores will, I am confident, reveal a larger number of 

 identical forms than those enumerated in the above list. The 

 Naticidse and Pectunculidse, two families requiring acute revision, 

 appear more especially to be intimately related in their specific 

 forms. 



