EASTERN TROVINCE SOUTHERN REGION SPECIES. 371 



aperture rounded, contracted by three teeth ; peristome heavy, broad, 

 white, hardly reflected near the basal extremity, quite on the edge, 

 armed with two short, incurving teeth, separated by a small, rounded 

 sinus ; on the columella there is a tooth-like fold, square, projecting 

 across the aperture, its extremities joining those of the peristome ; an 

 internal transverse tubercle on the base of the shell. Greater diameter 

 8J, lesser 7°*"' ; height, 3'"'". 



Helix Mooreana, W. G. Binney, Proc. Acad. Nat. Sci. Philad., 1857, 184 ; Terr. Moll., 

 iv, 80, pi. Ixxviii.tig. 24 ; L. & Fr.-W. Sh., i, 95 (1869).— Fischer and Crosse, 

 Moll. Mex. et Gnat., 275 (1870). — Pfeiffer, Mon. Hel. Viv., iv, 52. 



Dwdalochihi Mooreana, Tryox, Am. Jonrn. Conch., iii, 64 (1867). 



Helix thoJus, W. G. Binney, Proc. Acad. Nat. Sci. Philad., 1857, 186; Terr. Moll., iv, 

 81, pi. Ixxvii, fig. 21 ; L. & Fr.-W. Sh., 1. c, 95*.— Pfeiffer, Mon. Hel. Viv., 

 iv, 351. 



Dwdalochila Ihohis,, Tryon, Am. Journ. Couch., iii, 64 (1867). 



Polygyra Mooreana, W. G. Binney, Terr. Moll., v, 271. 



Texan Subregion, Washington and Bosque County, Texas ; also in 

 the neighboring Mexican States. < 



The specimens from which the descriptions of Mooreana and tholus 

 were drawn are widely different, but a study of a large suite of individ- 

 uals leads one to doubt their specific distinction. Although I now refer 

 P. tholus to 3Iooreana, I here repeat the original description and fig- 

 ure : 



Shell broadly umbilicated, depressed -globose, rather solid, white, 

 shining, ribbed above, smoother below ; spire obtuse, little fig. 406. 

 elevated, rounded ; whorls 7, convex, the upper ones 

 more flattened, the last bluntly carinated; carina not 

 reaching the peristome; base parallel to the suture; um- 

 bilicus broad, half the larger diameter of the shell, show- 

 ing two and a half deeply grooved whorls plainly, the 

 others rapidly retreating towards the apex; aperture 

 very oblique, semicircular, removed from the axis of the 

 shell, bordered with a scarcely reflected, white, heavy 

 peristome, grooved behind, and armed with two stout teeth near the 

 basal extremity, broadly reflected at the junction with the body-whorl; 

 on the parietal wall of the aperture is a white fold, hardly connecting 

 the extremities of the peristome, and projecting across the aperture 

 into an acute point; an internal transverse tubercle on the base of 

 the shell. Greater diameter 11, lesser 9""" ; height, 4'""'. 



The aperture of this curious shell {tholus) resembles that of P. fasti- 



