POLYGYRA. 271 



la the Texan Subregion in Texas and the neighboring Mexican State of 

 Taraaulipas. 



Animal brownish, or dingy white ; eye-peduncles darker, sheaths visible by 

 a dark line, much enlarged at tip. 



There is a variety larger, with 6 whorls, and with a brown band revolving 

 above the periphery. 



Jaw wide, low, slightly arcuate, ends blunt, with 10 decided ribs, denticulat- 

 ing either margin. 



Lingual membrane, as usual in the genus. Teeth 26 — 1 — 26, with 11 lat- 

 erals. (PL VI. Fig. G.j 



Polygyra triodontoides, Bland. 



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

 with partially obsolete rib-like striae above ; base convex, smooth ; spire short ; 

 whorls 5, somewhat convex, the last plicately ribbed near the aper- 

 ture, deflexed anteriorly ; aperture roundly lunate, oblique, con- 

 tracted ; 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 P.triodon- 

 apart. Greater diameter 9^, lesser 8 mill. ; height, 5 mill. 



Helix triodontoides, Bland, Ann. N. Y. Lye, VII. 424, PL IV. Figs. 11, 12 



(1861). — W. G. Binney, L. & Fr.-W. Sh., I. 94 (1869). 

 Helix Texasiana, W. G. Binney, Terr. Moll., IV. 79, PI. LXXVIII. Fig. 18. 

 Dcedalochila triodontoides, Tryon, Am. Journ. Conch., III. 62 (1867). 



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 P. Texasiana, and does not 

 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 hirsutum. In that respect, as well as in the form of the 

 aperture, Moricand's shell is more closely allied to P. Mooreana, YV. G. Binn. 



Lingual membrane as in fastigans, cereolus, etc. 



Polygyra Mooreana, W. G. Binn. 



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

 depressed, obtusely rounded ; whorls 6, 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 stria? are less 

 distinct; at the umbilical region only one and a quarter whorl is visible, the 



