278 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Z'lriU alone sufficiently distinguishes it from its allies. The space behind the 

 peristome, and between it and the curved pit, showing the seat of the superior 

 tooth, is convex and smooth, the striie not extending over it. 



This species lias, in common with fasligcms and Troosliana, a thin, brown, 

 but more sparingly hirsute epidermis. I have noticed the tubercle within the 

 last whorl, near the aperture, in fastigans and Troosdana, but no such process 

 exists in the species now under consideration. In llazardi the inferior tooth 

 of the peristome, at its inner end, is continued back within the aperture, form- 

 ing a white erect lamella on the floor of the whorl, parallel with, and leaving a 

 narrow sinus between it and tlie inner wall, to which it is joined at its extrem- 

 ity, about two and a half millimetres from the edge of the peristome. The 

 position of this lamella can be seen throu<>h the shell. 



Jaw as usual in the genus ; ribs numerous. 



Lingual membrane (PI. VI. Fig. O) has 16—1—16 teeth, with 8 laterals. 

 At least three of the transition teeth, or first marginals, have no bifurcation to 

 the inner cutting point. Beyond these, the mai-ginals have the point bifid. 



Genitalia unobserved. 



Polygyra oppilata, Moricand. 



Shell umbilicated, depressed, delicately striate, subpellucid, light horn-color 



or white ; spire scarcely elevated ; whorls 5, rather convex, gradually increas- 



y- ing, the last deflected at the aperture, inflated below, constricted 



behind the peristome ; umbilicus at first widened, then narrow, 



pervious ; aperture diagonal, Innately circular, ringent ; peristome 



briefly reflected, its terminations joined by a tongue-shaped, enter- 



■ ''^''"'"'"- ing, two-forked callus, the right margin subequally bidentate. 



Greater diameter 7, lesser 6 mill. ; height, 3 mill. 



Helix oppilata, Moricand, Test. Noviss., I. 8. — Pfeiffer, Mon. Ilel. Viv., III. 

 264; IV. 314.— W. G. Binney, L. & Fr.-W. Sh., I. 101, Fig. 177 (1869).— 

 Fischer and Crosse, Moll. Mex. et Guat., 287 (1870). 



The specimen figured is from Yucatan ; Pfeiffer on Shuttle-worth's authority 

 refers to Florida a var. /3 with a somewhat more elevated spire, 5| Avhorls, 

 and 8| mill, in the greater diameter. The specimen dissected by me is from 

 Cedar Keys. 



The above figure is referred to impUcata, Beck, by Crosse and Fischer, 1. c. 



Lingual membrane (PI. XVI. Fig. D) as usual in the genus. The inner 

 marginals have simple cutting points. 



Polygyra Dorfeuilliana, Lea. 



Shell rimately umbilicated, discoidal, slightly convex above, flattened below, 

 light horn-colored, striated, below smoother and with minute revolving lines ; 

 spire not much elevated; whorls 6, flattened, gradually increasing, the last 



