158 NEW UNIONID^, MELANID^, ETC. 



Planorbis Wheatleti. pi. 23, fig. 71. 



Test^ parva, tenebroso-cornea, planukta, obsolete striata, biearinata, superne depressa, inferne late et pro- 

 fundite umbilicata ; anfraotibus quinis, superne obtuse carinata, inferne acute carinata; apertura 

 albida, crassa et valde constricta, intus sesdentata. 



Shell large, dark horn-colored, flattened, obscurely striate, bicarinate, depressed 

 above, deeply and widely umbilicate below ; whorls five, obtusely carinate above and 

 acutely carinate below; aperture whitish, very thick and very much constricted; six- 

 toothed within. 



Proc. Acad. Nat. Sci., 1858, p. 41. 



Eah. — Cotoma Creek, Montgomery Co., Alab., C. M. Wheatley. 

 My cabinet and cabinet of Mr. Wheatley. 

 Diam. -28 inch. 



Bemarhs.— This, belongs to a group of which P. armigerus, Say, may be considered 

 the type, and which is so widely distributed over the Eastern and "Western States. 

 The principal character of both these species is in the position of the teeth, which 

 are internal and stretching nearly across the cavity of the whorl. P. Wheatleyi has 

 a very remarkable cord-like enlargement on the outer lip, which enlargement is 

 whitish, striate and in some specimens slightly undulating. The lip itself is thickened, 

 reflected and white with a dark line along the edge. The inner lip is thickened and 

 dark colored. The umbilical region is wide, sharply carinate on the edge and pre- 

 sents all the whorls to view. The striae are very fine. On the superior part of the 

 whorls there are, in some specimens, impressions which are of a darker horn-color. 

 The teeth are two on the pillar side and four on the opposite side, placed about one- 

 third of the whorl from the aperture. The largest is placed obliquely on the pillar 

 side, stretching nearly across it, is thin, lamellar and curved. Immediately below it 

 is a very small one. The four opposite teeth are rather small and lamellar. Two of 

 them point inwardly and two (the alternate ones) are across the whorl. The largest 

 one of these four is nearly in the centre, and is slightly curved. In this armature it 

 will be observed that there is a strong resemblance to that of armigerus, even in the 

 number of the teeth ; for, although Mr. Say states that " the throat is armed with five 

 teeth," there are in reality, in all perfect specimens of his species, six, the superior 

 one (the fourth on the side of " the labrum ") being distinctly visible even from the 

 outside in some of my specimens. The position of this armature is not so far in the 

 throat of armigerus, usually not more than the fourth of a whorl. The general appear- 

 ance of Wheatleyi is very different. It is more like hicarinatus. Say, having two very 

 distinct carinas, while armigerus has none, which I have ever seen, although Mr. Say 

 describes it as " obtusely carinate above." The enlargement, like a cord or collar 

 round the exterior portion of the aperture, is very remarkable, and a somewhat simi- 

 lar enlargement may be observed on the whorls to have taken place when the indi- 

 vidual was about half grown. 



