310 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



412 ; in CHEMNITZ, ed. 2, I. 364, PI. LXIV. Figs. 7-9. REEVE, Con. Icon., 



No. 686 (1852). W. G. BINNEY, L. & Fr.-W. Sh., I. 131 (1S69). 

 Helix tridentata, BINNEY, Pt. Bost. Journ. Nat. Hist., III. 382, PI. XVIII. Fig. 



3 (1840); Terr. Moll., II. 183, PI. XXVIII. W. G. BINNEY, Terr. Moll., 



IV. 72. 

 Triodopsis fallax, TRYON, Amer. Journ. Conch., III. 51 (1867). 



From Canada to Texas and Florida, all over the Eastern Province. 



Nearly allied to T. tridentata, but in this the spire is more elevated, and 

 sometimes has 6 full volutions. There is a deep groove behind the peristome, 

 contracting the aperture ; the peristome is widely reflected, and directed in- 

 wards, forming a basin-shaped mouth ; the upper tooth on the peristome is 

 broader, sometimes bifid, and even trifid, and very much inflected ; the parietal 

 tooth extends quite to the base of the shell, and unites with the extremity of 

 the peristome ; the aperture is nearly filled up by the teeth and the contraction 

 of the peristome. 



Animal as in T. tridentata (see B. J. N. H., I. PI. XVIIL). 



Jaw as usual in the genus ; 14 ribs. 



Lingual membrane (PI. VII. Fig. L) has about 40 1 40 teeth ; 12 perfect 

 laterals. This (not tridenlata) had no bifurcation to the inner cutting point of 

 the transition teeth (thirteenth and fourteenth teeth), at least on the portion 

 of the membrane examined by me. 



Genitalia (PI. XV. Fig. B) as in tridentata, but the duct of the genital blad- 

 der is of equal size throughout its length, an unimportant, even if constant 

 difference. 



Triodopsis introferens, BLAND. 



Shell umbilicate, globose, depressed, thin, with rib-like striae, yellowish horn- 

 colored ; spire convex ; whorls 6, moderately convex, the last scarcely descend- 

 ing, much constricted at the aperture, with two exterior pits, sub- 

 2l~' angular at the periphery, convex beneath, grooved within the 



umbilicus ; aperture oblique, lunate, with a well-developed, arcu- 

 ate parietal tooth ; peristome white, thickened within, reflected ; 

 on the right margin an obtuse inflected tooth, at the base a sub- 

 T. introferens. marginal lamelliform tooth, with transverse tubercle in the cen- 

 tre; the basal lamella continued within the aperture, where it 

 forms a strong white tubercle. Greater diameter 15, lesser 13 mill.; height, 7 

 mill. 



Helix introferens, BLAND, Ann. N. Y. Lye., VII. 117, PI. IV. Figs. 3, 4 (1860). 



-W. G. BINNEY, L. & Fr.-W. Sh., L 132 (1869). 

 Triodopsis introferens, TRYON, Am. Journ. Couch., III. 51 (1867). 



Gaston County, North Carolina ; Salem, North Carolina. Valley of the 

 Holston, Tennessee ; Fanning County, Georgia ; Aiken, South Carolina ; 

 Georgetown, District of Columbia. A species of the Cumberland Subregion. 



