Bimieifs Description of a Helix. 241 



Art. XVIIL— description OF A SPECIES OF HELIX, NEWLY 

 OBSERVED IN THE UxNITED STATES. Br Amos Binnet. 

 (Read December 1, 1841.) 



HELIX SUB-PLANA. 



H. testA discoided, fuliginosa, aut corneo-rufescente, nitente; spira depressa; 

 anfractibus quinque vel eex ; apertura semilunari, transverBa ; labro simplici, 

 acuto; basi piano; umbilico parvo. 



Description. 



Animal. Not hitherto noticed. 



Shell. Flattened, planulate above and beneath ; epidermis 

 brownish or smoky horn-color, shining ; whorls five and a 

 half, those nearest the apex striated transversely with very mi- 

 nute and delicate wrinkles ; suture distinct, not much im- 

 pressed ; aperture transverse, not expanded, the plane of the 

 aperture making nearly a right angle with the plane of the 

 base of the shell ; lip simple, thin, acute ; base flattened, um- 

 bilical region a little impressed ; umbilicus very small, round 

 and deep, not exhibiting the volutions. Greatest transverse 

 diameter less than three-fourths of an inch. 



Geographical Distribution. Found hitherto only in the 

 mountainous region of eastern Tennessee. 



Remarks. The only American species which this shell 

 can be said to resemble, is Helix inornata, which in size and 

 color is quite like it, and at first sight may be taken for it. It 

 differs from it in the following particulars. The upper and 

 lower surface are both more flattened, and the outline is a more 

 perfect circle. The number of whorls in specimens of the 

 same size is greater by nearly one volution. The surface of 

 the whorls is less rounded ; the last whorl expands but very 

 little towards the aperture ; the base is broader, less indented, 

 and very flat ; the umbilicus is rounder, and better defined ; 

 and the aperture is not thickened within by a white testa- 

 ceous deposit. 



I have seen but two specimens, which were brought from 

 Tennessee by Mr. S. S. Haldeman. 

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