1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 451 



with a slight constriction behind it; umbilicus moderate, deep, exhibit- 

 ing but little more than one of the whorls. Greater diameter 15 lesser 

 13 mM ; height, 7 mm . Kiowa Station, about thirty specimens, mostly dead. 

 Limestone Gap, two dead specimens. Another badly bleached shell was 

 obtained not far from Eufaula. 



Dr. E. E, C. Stearns considers this as a close ally of some of the 

 smaller forms of M. thyroides. It seems to me to be more nearly re- 

 lated to M. sayi. Its wider umbilicus, more transverse aperture, solider 

 texture, and less elevation distinguish it from thyroides; it is more de- 

 pressed and has a more transverse aperture and narrower umbilicus 

 than any forms of sayi I have seen, and its soft parts differ essentially 

 from those of either. According to Mr. Pilsbry the jaw has 9 ribs (sayi 

 having 13 to 16 aud thyroides 13), the teeth have fewer laterals than 

 sayi, and the inner cusp is bifid on the marginals, while in sayi it is en- 

 tire. 

 Heliccdiscus fimbriatus Wetherby. 



A small variety wanting the epidermal fringe, aud nearly destitute 

 of the revolving ridges described by its author. Thousands of speci- 

 mens were found, mostly dead, under slabs of sandstone on the 

 mountains near Fort Gibson, and a few were taken at Limestone Gap. 

 So far as I know, this is an entirely new locality ior this species, as it 

 has been credited heretofore only to the Cumberland subregion. I be- 

 lieve that a careful search throughout the Ozark Mouutains and north- 

 ern Texas will discover most of the species that have hitherto been 

 supposed to belong only to the Appalachian chain. Most of the speci- 

 mens found measured only from 3 to 4 mm in diameter, 



Helicodiscus lineatus Say. 



Fort Gibson; Limestone Gap. 

 Selenites concava Say. 



Fort Gibson, a few shells. 

 Zonites friabilis W. G. Biuney. 



Abundant on limestone mountains near Fort Gibson and Tahlequah, 

 and remarkably dark colored. 



Zonites ligerus Say. 



Fort Gibson. 

 Zonites acerra Lewis. 



Low wet woods, Fort Gibson, with Zonites ligerus, Triodopsis injlecta, 

 aud the ribbed variety of Patula attenuata. Binney makes this merely 

 a variety of Zonites demissus, but unless there are forms that connect the 

 two it seems to me to be as distinct as most of the species of Z mites. 

 Zonites arboreus Say. 



Eufaula. 

 Zonites radiatulus Alder. 



Limestone Gap. 



