292 a" MANUAL OF AMERICAN LAND SHELLS. 



25 teeth ; 10 laterals. The iuuer cutting point is bifid after the tenth 

 tooth. 



Genitalia (Terr. Moll., V, Plate XV, Fig. D) : The penis sac is long, 

 cylindrical, receiving the vas deferens and retractor muscle at its sum- 

 mit; genital bladder small, globular, with along duct, which is nar- 

 row above but below its middle gradually enlarges to greater than 

 the width of the bhidder. The details of the size of the genital blad- 

 der and Its duct seem to offer an excellent specific character to the 

 members of this group of THodopsis. 



Trio«lo|>si«>> fallax, Say. 



Shell umbili(;ated, depressed-globose, with rib-like striae, reddish 

 ]<-i(ijii4. h()rn-c<)l()re<l ; spire convex ; whorls G, rather convex, the 

 last deflected anteriorly, constricted; aperture trilobed, 

 contracted by a large, oblique, tongue-shaped, arcuately 

 entering tooth on the i)arietal wall; peristome reflected, 

 thickened within, white, with 2 teeth, the upper one bend- 

 ing inward not on the edge, the other sub-basal. Greater 

 T.faiiax. diameter 13, lesser 11"""; height, 7^""". 



Eelix fallax, Say, Journ. Pliila. Afiul., v, 119 (1825) ; Binney's ed.,27. — De Kay, N. 



Y. Moll., 28,1.1. iii, {\g. 2:5 (184;0-— Pfkiffku, Mou. IK'l. Viv., i,412; in Chem 



NIT/, (Ml. 2, i, ;5(i4, i>l. ].\i V, iigs. 7-9.— Reeve, Con. Icon., No. G«G (1852).— W. G. 



BiNNKY, L. & Fr.-VV. Sh., i, i:?l (18(;;)). 

 Helix tridentdla, Binxey, Pr. Bost. Journ. Nat. lli.st., lii, 382, pi. xviii, fig. 3(1840) ; Terr. 



Moll., ii, 183, pi. xxviii.— W. G. Binney, Terr. Moll., iv, 72. 

 Triodopsia fallax, Tkyon, Anier. Journ. Concb.,iii, 51 (1867). — W. G. Binney, Terr. 



Moll., V, 309. 



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



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

 and sometimes has G full volutions. There is a deep groove behind the 

 peristome, contracting the aperture; the peristome is widely reflected 

 and directed inwards, forming a basin-shaped mouth; the upper tooth 

 on the peristome is broader, sometimes bifid, and even trifid, and very 

 mu(;h inflected; the parietal tooth extends quite to the base of the 

 shell and unites with the extremity of the peristome;* the ajierture is 

 nearly filled up by the teeth and the contraction of the peristome. 



Animal as in T. ttidentata (see B. J. N. H., I, Plate XVIII). 



Jaw as usual in the genus; 14 ribs. 



Lingual membrane (Terr. Moll., V, Plate VII, Fig. L) has about 

 40-1-40 teeth; 12 perfect laterals. This (not tridentata) had no bifur- 



Not, however, iu the shell figured. 



