• TRTODOrSIS. 307 



Xohtrcvui clausa, Rafinesquk, Eiiuincration, &c., 3 (1831) ; cd. Binney and 



TiiYON, 68. 

 Isogiwmostovia infccta, Tryon, Am. Jouni. Conch., III. 54 (1867). 



A Post-])leioccnc species, now found in the Interior Rej^ion, from Texas to 

 the Appnhichian Chain in Pennsylvania and New York; from Sea Islands of 

 Geortria throu<ji;h the Northwestern States. 



The large specimen figured on p. 306 is from University Place, Tennessee, 

 ■where the species seems most developed. 



Animal dark hluish slate-color ; head, eye-peduncles, and tentacles almost 

 black ; eye-peduncles long and slender ; foot narrow, in length more than twice 

 the diameter of the shell, terminating in an acute angle (see Bost. Journ. 

 N. H., I. PI. IX.). 



Jaw thick, short, broad, arched, of almost uniform width quite to the blunt 

 ends; with 14 stout, crowded ribs, visible on both anterior and posterior sur- 

 face and denticulatinof either margin. 



T. injiecta (PL VII. Fig. S) has 22—1—22 teeth on its lingual membrane ; 

 7 perfect laterals. This and the following species have inner marginal teeth, 

 with simple, not bifid, cutting points (c). It was bifid in the twenty-first tooth 

 of one specimen examined, simple in the twenty-second, and bifid in the twenty- 

 third, and all beyond. There were over 23 — 1 — 23 teeth on this membrane. 



Genitalia as in T. Rugeli. 



Triodopsis Rugeli, Shuttleworth. 



Shell imperforate, orbicularly convex, with granulate striations and few hairs, 

 waxen horn-color ; spire short, obtuse ; whorls 5^, rather convex, the last sud- 

 denly falling in front, and strongly contracted at the aper- 

 ture ; aperture depressed, narrowed by a tongue-shaped, 

 flexuose, strong, parietal denticle ; peristome reflected, within 

 thickened, its right termination with a large, obtuse, very 

 deeply seated tooth (whose position is marked on the exterior 

 of the shell by a groove or pit), the basal terminus furnished 

 with a smaller, transverse, submarginal denticle. Greater 

 diameter 13, lesser \l\ mill. ; height, Q\ mill. T. iJwg^eW, enlarged. 



Helix Rtigeli, Shuttleworth, Bern. Mittheil., 1852, 198. — Pfeiffer, Mon. 



Hel. Viv., III. 268. —Gould in Terr. Moll., III. 18.— W. G. Binney, Terr. 



Moll., IV. 60, PI. LXXVIIl. Fig. 15; L. & Fr.-W. Sh., I. 129 (1869).— 



Bland, Ann. N. Y. Lye, VII. 426. 

 Isognomostoma Rugeli, Tryon, Am. Journ. Conch., III. 55 (1867). 



Tennessee, North Carolina, Wliitley County, Kentucky. A species of the 

 Cumberland Subrejjion. 



It is in most respects similar to the preceding species, and would be mistaken 

 for it unless the aperture be examined. The position of the upper tooth of the 



