136 FOSSIL GENERA. 



largest on the varices, and giving the shell a cellular aspect; 

 beak much curved ; color cinereous ; aperture small, obovate, 

 purplish within. Inhabits oyster beds. 



M. OSTREARUM. Fusiform, with revolving ribs alternated in size, 

 and with longitudinal wrinkles; spire elevated, scalarilbrm ; base 

 umbilicated ; within livid. Occurs with the preceding. 



Fossil Genera. 



PTEROHYTIS, Conrad. Genus not characterized. The type has 

 lamellar varices like Cerostoma foliatum but more numerous than 

 in that group, and the outer lip has a tooth. I think it may be 

 safely relegated to Phyllonotus, Swains. 



P. UMBRIFER, Com. PL 70, fig. 429. Miocene, Virginia. 



ODONTOPOLYS, Gabb. Resembles the subgenus Pteronotus in 

 having three varices on each whorl but distinguished by the 

 crenulations of the outer lip and by having two transverse plaits 

 or folds on the middle of the columella. 



O. COMPSORHYTIS, Gabb. PI. 70, fig. 430. Eocene, Wheelock, Texan. 



(ienus TYPHIS, Moritfort. 



The ascending tube which is the distinguishing feature of the 

 shells of this genus is occupied by an extension of the mantle 

 margin of the animal. 



The operculum is ovate, with apical nucleus, like that of Mnrex. 



There are several European Eocene species. 



This genus is monographed both by Sowerby and Reeve. 



T. TETRAPTERUS, Bronii. PI. 30, figs. 290-292. 



Flesh color. Length, -5 inch. 



Confined to the Mediterranean, where it is widely distributed. 

 Miocene to post-pliocene of Southern Europe. 



T. ARCUATUS, Hinds. PI. 30, figs. 293, 297. 



The tubes are incurved so as to approach the preceding whorl. 

 Somewhat smaller than the preceding, but not very dissimilar. 



Cape of Good Hope, Japan, China. 



T. Japonicus, A. Adams, is made a synonym in Sowb. Thes. 



