TRIODOPSIS. 311 



Tliis slioll is closely allied to vultuosa and also to fallax. It differs from the 

 latter in the narrower umbilicus, which only shows the penultimate whorl ; in 

 the groove in the last whorl within the umbilical opening, the character of the 

 basal tooth, and the internal tubercle, which does not prevail in fallax and its 

 inunediate allies tridentata and Hopetonensis. In inlroferens the upper tooth is 

 less deeply seated and less inflected, and the basal one is broader and more 

 elevated than in vultuosa^ the parietal tooth is more arcuate, being indeed sub- 

 angular, but is without the indication, noticeable in vultuosa, of a callus extend- 

 ing from its lower termination towards the upper angle of the peristome. T. 

 vul/uosa is even smaller than the var. minor of this species, which is only 11 

 mill, in diameter. 



Jaw as usual in the genus ; over 14 ribs. 



Lingual membrane (PI. XVI. Fig. C). 



Triodopsis Hopetonensis, Shuttleworth. 



Shell with a narrow, scarcely pervious umbilicus, depressed-globose, with 

 numerous rib-like striae, olive horn-color; spire obtuse, convex; whorls 5|, rather 

 convex, the last scarcely deflected in front, constricted 

 at the aperture ; aperture lunar, tridentate ; a mod- '^' 



erate, tongue-shaped, slightly entering parietal denti- 

 cle ; peristome reflected, within thickened with a white, 

 light callus, its right margin with a small, somewhat 



*= . "^ ® ' T. Hopetonensis. 



anterior denticle, its basal terminus with a marginal 

 denticle. Greater diameter 13, lesser 11 mill. ; height, 6 mill. 



Helix Hopetonensis, Shuttleworth, Bern. Mitt., 1852, 198. — Reeve, Con. Icon., 



No. 709 (1852). — Pfeiffer, Mon. Hel. Viv., III. 263 ; in Chemnitz, ed. II. 



420, PL CXLVIII. Figs. 17, 18 (PI. LXIV. Figs. 7 - 9 ?) . — Gould, Terr. 



Moll., III. 17. —W. G. Binney, Terr. Moll., IV. 72, PI. LXXVII. Fig. 16 ; 



L. & Fr.-W. Sh., I. 132, Fig. 224 (1869). 

 Helix, tridentata, var., Binney in Bost. Journ. Nat. Hist., III. 382, PI. XVIII. 



Fig. 2. — Ferussac, Hist., PI. LI. Fig. 3, small figure on the left. 

 Helix tridentata, var,, ephahus, Say, of Ravenel's Cat., 9 (1834), no descr. 

 Triodopsis Hoptetonensis, Tryon, Am. Journ. Conch., III. 52 (1867). 



A species of the Florida Subregion, ranging as far north as Charleston, 

 South Carolina, as far south as Fort George, St. John's River. 



It differs from T. fallax in its smaller, scarcely pervious umbilicus, its deeper 

 color, lighter peristome, and denticles being more widely separated. 



Jaw as usual in the genus; over 10 ribs. 



The lingual membrane (PI. VII. Fig. N) has 27 — 1 — 27 teeth, as far as I can 

 judge from an imperfect membrane. There are 7 laterals, the eighth tooth 

 having its inner cutting point bifid. 



Genitalia (PI. XV. Fig. A) readily distinguished from those oi fallax, triden- 

 tata, and others of the group by the length and cylindrical form of the genital 



