302 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



becomes gradually shorter, until the true marginals are reached. These last 

 are low, wide, the reflection equalling the base of attachment, the inner cutting 

 point being greatly developed, long, oblique, bluntly bifid, and the inner bifur- 

 cation the shorter of the two ; the outer cusp is very short, blunt, sometimes also 

 bifid. In this species the tenth is the first lateral showing decided modification ; 

 the fourteenth tooth has its inner point bifid ; the seventeenth tooth is a decided 

 marginal. The transition from laterals to marginals is so gradual that it is 

 often difficult to give the number of perfect laterals. In many cases, therefore, 

 the number given by me must be considered as only approximately correct. 

 There is great variation in the denticulation of the marginal teeth. 



The general character of the dentition of the other species is about the same 

 as in appressa. I found great difficulty in detecting the side cutting points in 

 several species, especially tridentata and palliata. In some species I did not 

 find the transition teeth or inner marginals with bifid cutting point. Helix per- 

 sonata is the only European species of this subgenus, but no figure of its den- 

 tition has been published to compare with that of our species. The same is 

 true of the two Central American species known. 



Triodopsis palliata, SAY. 

 Vol. III. PI. XIV. 



Shell with the umbilicus closed, thin, depressed ; epidermis dark brown or 

 chestnut-color and rough with minute, acute projections and stiff hairs ; whorls 

 5, flattened above and rounded below, with numerous very fine, oblique striae ; 

 aperture three-lobed, much contracted by the peristome and teeth ; peristome 

 white, sometimes edged with brown, widely reflected, with two projecting teeth 

 on the inner margin, the one near its junction with the body-whorl acute and 

 prominent, the other, on the basal portion, long, lamellar, and but little promi- 

 nent; parietal wall with a very prominent, white, curved tooth, projecting 

 nearly perpendicularly from the shell, and forming one boundary of the aper- 

 ture ; umbilicus covered with a white callus, the continuation of the reflected 

 peristome ; base convex. Greater diameter 21, lesser 18 mill. ; height, 

 10 mill. 



Helix palliata, SAY, Journ. Phila. Acad., II. 152(1821); BINNEY'S ed. 10. 

 BINNEY, Bost. Journ. Nat. Hist., III. 353, PL VII. (1840); Terr. Moll., II. 

 136, part, PI. XIV. ADAMS, Vermont Mollusca, 159 (1842). LEIDY, T. M. 

 U. S., I. 253, PL VII. Fig. 8 (1851), anat. DEKAY, N. Y. Moll., 33, PL III. 

 Fig. 36 (excl. a, b) (1843), excl. syn. pars. PFEIFFEK, Mon. Hel. Viv., I. 

 316 ; in CHEMNITZ, ed. 2, I. 359, PL LXII. Figs. 15, 16 (1849). MRS. GRAY, 

 Fig. Moll. An., PL CXCIII. Fig. 8, ex Bost. Journ. (no descr.). DESHAYES 

 in FEE., I. 144 (excl. var.). REEVE, Con. Icon., No. 678. W. G. BINNEY, 

 Terr. Moll., IV. 56; L. & Fr.-W. Sh., I. 124 (1869). BLAND, Ann. N. Y. 

 Lye., VII. 441. MORSE, Amer. Nat, I. 150, Figs. 10, 11 (1867). GOULD 

 and BINNEY, Inv. of Mass., ed. 2, 420 (1870). 



