INSTITUTE OF SCIEN'CE, PHILADELPHIA. 215 



M. P. R. 



Nassa acuta, Say (S. M.) 00 



Nassa trivittata, Say(S. M.) o o 



Nassa vibex, Say (S. ) 00 



Iljanassa obsoleta, Say (S. M.) 000 



Anachis avara, Say, var. semiplicata, Stearns (S. M.) o 



Anachis camax, Dall (S ) o 



Anachis obesa, C. B. Ads. (S. M.) o 



Astyris lunata, Say (S. M.) o o 



Eupleura caudata, Say (S.) 00 



Urosalpinx cinereus, Say (S. M.) o 



Scala lineata. Say (S.) o ° 



Scala angulata, Say (S. M.) o 



Eulima conoidea, K. & S. (S ) 000 



Pyramidella arenosa, Conr. (S.) 000 



Turbonilla reticulata, C. B. Ads. (S. M.) o o 



Turbonilla multicostata, C. B. Ads. (S.) ■ o o 



Turbonilla interrupts, Totten (S.) o o 



Turbonilla punicea, Dall (S.) o 



Odostomia seminuda, C. B. Ads. (S.) o o 



Sella terebrans, C. B. Ads. (S.) 000 



Vermicularia spirata, Phil. (IVI.) o o 



Crepidula convexa. Say (S. M.) 00 



Crepidula fornicata, Linn^ (M.) o o 



Crepidula plana, Say (S. M.) o o 



Neverita duplicata, Say (S. IVI.) 000 



Natica pusilla, Say (S. M.) 000 



Calliostoma erosum Dall, n. sp. (S.) ? 



Fissuridea alternata. Say (S. M.) 00 



In the discussion of these tables, if we adopt the old-fashioned method, 

 it appears that, throwing all the doubtful species into the category of extinct 

 forms, we have from the Waccamaw beds 125 out of 180 species still found 

 living, or about 70 per cent. ; while from the Croatan beds we have 80 out 

 of 96 species represented in the recent fauna, or over 83 per cent. By 

 this method the Pliocene character of the beds is obvious, according to the 

 numerical rule. 



If, however, we prefer to adopt the more modern and rational method of 

 a comparison with standard faunas, we arrive at practically the same result. 

 Of the 180 species of the Waccamaw beds, 2 have been hitherto regarded 

 as strictly Miocene, 16 are known as cominon to Miocene and Pliocene faunas 

 elsewhere, 17 are characteristic of Pliocene faunas elsewhere; 7 are new to 

 science, and 13 are of doubtful or contestable range. Of the remainder, 51 

 are known to be common to Miocene, Pliocene and recent faunas, 64 to Plio- 

 cene and recent faunas, and 9 have hitherto been known only in the recent 

 state. 



Eliminating the 5 1 uncharacteristic species, together with 20 which are 

 doubtful or new, we have remaining 109 species, of which 2 have been known 

 only as Miocene, 17 only as Pliocene, and 9 as recent ; or 90 which are known 



