INSTITUTE OF SCIENCE, PHILADELPHIA. 445 



ola beds, Chipola River, Calhoun Co., and the lower bed at Alum Bluff, 

 Appalachicola River, Florida, Burns. 



The denticulations of the posterior orifice are feeble compared with most 

 of the dentate species. A more cylindrical variety was represented by a few 

 specimens, among many, from the Chipola River, and most of those from Alum 

 Bluff, but the difference is hardly great enough to dignify by applying a 

 name to it. 



Oadulus thallus Conrad. 



Dentalhim thallus Conr., Journ. Acad. Nat. Sci. vii. p. 142, 1834; lb., Fos. Shells of the 

 Tert. Form., p. 78, pi. 44, fig. 5, 1S45 ; Tuomey and Holmes, Pleioc. Fos. S. Car., p. 106, 

 pi. 25, fig. 3, 1S57 ; Emmons, Rep. Geol. Surv. N. Car., p. 274, fig. 189, 185S. 



Chesapeake Miocene of Jones's Wharf, Patuxent River, Maryland, Harris ; 

 of the James and York Rivers, Virginia, Lea, Conrad, etc. ; of Duplin Co., 

 N. Carolina, Burns ; of South Carolina, Tuomey and Holmes, and of the upper 

 bed at Alum Bluff, Florida, Burns. 



This is the commonest and most widespread species of the Newer Mio- 

 cene. It is very close in general form to the recent C. carolinensis Bush, but 

 the latter has a circular anterior aperture, and the denticulations of the pos- 

 terior orifice are much deeper and more irregular. Meyer has referred to this 

 .species (Proc. Acad. Nat. Sci. Phila. 1884, p. 112) the C. paiidionis Werr'iW, 

 and to the latter Jeffreys has applied the name C. Olivii Scacchi. But C. Olivii 

 and pandionis are very different species, and the genuine pandionis is shorter 

 and less attenuated behind, and has a circular and not an oval anterior 

 aperture. 



Oadulus sp. indet. 



Older Miocene of the Chipola beds, Calhoun County, Florida, Burns. 



This species, which, though evidently different from the two others named 

 from the Chipola beds, is only represented by half-grown specimens, has its 

 posterior end attenuated and a good deal curved and shows a dorsal, ventral 

 and two lateral notches at the margin ; the shell is circular in section, increas- 

 ing gradually and evenly in diameter forward to the end of the growth attained, 

 a length of about 5.0 mm. The maximum diameter is about 1.25 mm. 



Oadulus quadridentatus Dall. 



C. quadridentatus Dall, Bull. Mus. Comp. Zool. ix. p. 36, July, 1881. 



C. incisus Bush, Trans. Conn. Acad. Sci. vi. p. 471, pi. xlv. fig. 20, June, 1885 ; Dall, Bull. 



U. S. Nat. Mus. No. 37, p. 76, No. 26, pi. 41, fig. 20, 1889. 

 C. quadridentatus Dall, Blake Gastr., p. 428, pi. xxvil. fig. 5, 1889. 



Pliocene of the Caloosahatchie River, Florida (rare), Dall ; living on the 

 coast of the Southeastern United States from Cape Hatteras southward to the 

 west coast of Florida, to Fernando Noronha and the mouth of the Rio La 

 Plata, South America, U. S. Fish Commission. 



