From the Proceedings of the Academy of Natural Scienoes, October, 1867. 



Notes on American Land Shells. No. 2. 

 BY W. G. BINNEY. 



Helix (Poltgyra) acdte-dentata. Testa superne et subtus parum planata, 

 discoidea, albida, glabra ; anfractus 6 l^vigati, quorum quiuque aequaliter 

 accrescentes, apicem brevissimam, vix elevatam formantes ; ultimuspermagnus 

 inflatns, prope peristomata bis valde scrobiculatus, ad aperturam deflectus ; 

 Bubtus anfractus 1 J, ultimus ventricosus, alter rapide decrescens ; umbilicus par- 

 vus, profundus ; sutura impressa ; apertura parva, perobliqua, ringens ; peristoma 

 circulare, acutum, album, incrassatum, patulo-reflexum, marginibus callo albo, 

 dentiformi, emarginato, excavato conjunctis, dextro dentibus duobus horizon- 

 talibus, uno obtuso, alteri acutissimo intus armato, basali dente unico perpen<> 

 diculari in margine posito, munito. 



Diam. maj. 14, min. 11, alt. 4 mill. 



Specimen unicum in collectione Phillips conservatum in prorincia Mexicana 

 Cinaloa ripis fluminis Mazatlan collegit Gambel. 



This curious Helix differs from any hitherto known. It is readily distin- 

 guished by a white, shining, discoidal shell, curious aperture and internal 

 teeth. The upper surface is composed of six whorls, five of which regularly 

 increase from the spire, which is slightly elevated; the last is proportionally very 

 wide, inflated, and elevated above the others, almost to a level with the apex. 

 Below, one full ventricose whorl is visible, and more than half of another, 

 which rapidly decreases until it becomes lost in the small umbilicus. The 

 aperture is oblique, basin-shaped, furnished with four teeth ; of these one on 

 the parietal wall connecting the extremities of the peristome is broad, excavated 

 in the middle, angular, resembling that of H. Troostiana, Lea, (plicata. Say) • 

 on the basal portion of the peristome is another, situated on the edge, perpen- 

 dicular and short ; on the right lip, slightly removed within the aperture are 

 two slight elongated laminae, running horizontally, the lower one raised above 

 the whorl for some distance, thus forming a slender, spear-like point. Behind 

 the teeth on the outer whorl are two pits, between which the shell is pinched 

 into a sharp ridge joining the peristome. 



Helix (Polygyra) Loisa. Testa albido-cornea, tenuis, superne minute et 

 confertim striata, spira paululum elevata, sutura impressa, anfr. quinque, vix 

 convexiusculi, ultimus permagnus ; subtus inflata, nitida, vix perforata, anfr. 

 1^, ultimus ventricosus, prope peristoma bis valde scrobiculatus ; alter rapidis- 

 sime decrescens, apertura ringens, quinquedentata ; perist. acutum, album 

 incrassatum, patulo-reflexiusculum, marginibus callo albo, crasso, dentiformi 



1857.] 



