370 A MANUAL OF AMERICAN LAND SHELLS. 



Polyg^yra triodoiitoides, Bland. 



Shell umbilicated, globose- depressed, thin, subpellucid, pale horn- 

 colored, with partially obsolete rib-like strife above; base convex, 

 smooth; si)ire short; whorls 5, somewhat convex, the last 



Flo. 404. 7X7' ' 



plicately ribbed near the aperture, detiexed anteriorly; aper- 

 ture roundly lunate, oblique, contracted; peristome reflected, 

 callous, the margins joined by a sharp, linguiform, triangular, 

 tooth, the right with a tooth on the margin of the callus, 



basal with an oblique tooth, both teeth small and far apart. Greater 



diameter 9 J, lesser 8" '" ; height, 5"""^. 



Melix Modonfoides, Bland, Ann. N. Y. Lye, vii, 424, pi. iv, figs. 11, 12 (1861).— W. G. 



BiNNKY, L. &. Fr.-W. Sh., i, 94 (1869). 

 Helix Texasiaita, "NV. G. Binney, Terr. Moll., iv, 79, pi. Ixxviii, fig. 18. 

 Dn>dalocMla iriodontoides, Try'ON, Am. Journ. Conch., iii, 62 (1867). 

 Polygyra triodonloides, W. G. Binney^, Terr. Moll., v, 271. 



Corpus Christi and De Witt County, Texas, belonging, therefore, to 

 the Texan Subregion; but I have traced it northward into the Indian 

 Territory (Choctaw Nation). 



P. triodontoides is a more delicate shell than F. Texasiana, and does 

 not usually attain the same size. It is not as distinctly' ribbed, is 

 somewhat more elevated, and the aperture more round. The last 

 whorl is less devious at its termination beneath, the peristome teeth 

 are smaller and wide apart. In P. Texasiana they are close together, 

 and the space between them has much resemblance to the notch in 

 Stenotrema hirsufum. In that respect, as well as in the form of the 

 aperture, Moricand's shell is more closely allied to P. Mooreana^ W. G. 

 Binney. 



Lingual membrane as in fastigans, cereolus, &c. 



I*oIysy*'a Mooreaiia, W. G. Binney. 



Shell umbilicated, orbicular, globose, white, subcarinated ; spire more 



405 ^^' ^^^^ depressed, obtusely rounded ; whorls C, distinctly 



striated, hardly convex; suture impressed; below the 



carina the body-whorl is not rounded, but slants down 



to the base, which is parallel with the suture; below 



the striae are less distinct; at the umbilical region only 



one and a quarter whorl is visible, the outer one strongly 



cariuated so as to conceal a portion of the umbilicus and a great part 



of the remaining whorl ; the umbilicus is very small, but perforates 



the shell to the apex, showing all the volutions with the aid of a lens j 



