EASTERN PROVINCE INTERIOR REGION SPECIES. 271 



P. fastigans is larger thau Troostiana^ Razardi, .and BorfeuilUana; 

 it is most nearly allied to the first, and thongh it is connected with the 

 second, is wholly distinct from the last. The parietal tooth is more rec- 

 tangnlar than that of Troostiana, in which it is slightly emarginate 

 near the tip, but much more so in Hazardi, while the parietal tooth in 

 DorfeuilUana is rather quadrate. The teeth on the peristome in fastigans 

 and Troostiana are much alike as regards form, size, and position, the 

 superior one being the largest; both are larger and transverse in Dor. 

 feuilUana and in Hazardi, the infeiior one being the largest in the lat- 

 ter. Behind the peristome there are two small pits, showing the situa- 

 tion of the teeth in fastigans and Troostiana, while there is scarcely 

 more than a deep, well-marked constriction in DorfeuilUana. P. Troos- 

 tiana has a slight groove on the inner side of the last whorl, the ab- 

 sence of which in fastigans is noticed by Say; but I scarcely consider 

 that a good specific character. Fresh specimens of fastigans are, I 

 believe, covered with a very thin epidermis, on which hairs are spar- 

 ingly scattered ; the scars of the hairs may be detected, especially on 

 the last whorl, in denuded shells. 



P. fastigans has, at a short distance within the aperture, on the base 

 of the last whorl, a small, detached, erect, rounded tubercle, answering 

 probably the same purpose in the economy of the animal as the " ful- 

 crum" originally noticed by Mr. Lea (Observations, Vol. V, p. 80) in 

 Strenotrenia spinosum, though of a different construction. 



Jaw slightly arcuate, long, Ioav, with about 20 ribs on the anterior 

 surface, crenulating either margin. 



P. fastigans (Terr. Moll., V, Plate VI, Fig. H) has 21-1-21 teeth, 

 with 8 laterals on the lingual membrane. 



STE.\OTREMA, Raf. 



Animal heliciform, mantle subcentral; other characters as in Patula. 



Shell with the perforation covered, lenticular or globosely depressed, 

 hairy ; whorls 4^-6, the last anteriorly gibbous, shortly deflexed, tumid 

 below; spire somewhat elevated; peristome with a white, thickened 

 margin, briefly reflexed above, somewhat constricted in its basal por- 

 tion, usually sinuous and dentate, furnished with an internal transverse 

 tubercle on the floor of the base of the last whorl. 



A North American genus, meeting its greatest development in the 

 Cumberland Subregion. 



