270 [November, 



Descriptions of Species. 

 Natica Tuomyana, 



Shell subglobose, thick and solid ; spire not much elevated ; volutions four to 

 four and a half, convex, last one crossed by strong folds ; suture distinct or 

 slightly grooved ; surface marked with fine closely arranged lines of growth, 

 crossed by flat revolving bands ; aperture apparently ovate ; umbilicus very small 

 or only rudimentary. Length and breadth about -88 inch ; apical angle slightly 

 convex ; divergence about 110. 



We have seen but one specimen of this species, a portion of the body volution 

 of which is broken away. The outer lip seems to have been bevelled, and joins 

 the body whorl above, at an angle of about 90. The revolving bands are gene- 

 rally faint, and wider than the grooves between them on the upper part of the 

 whorls, but more distinct and about equal to, or smaller than, the depressions 

 near the middle and below. The inner lip is not callous in the umbilical region. 



This species may be at once distinguished from any other known to us from 

 the Nebraska formations, by its greater thickness, and the strong vertical folds 

 and revolving bands. We name it in honor of Prof. M. Tuomy, State Geologist 

 of Alabama and South Carolina. 



Locality and position. Mouth of Judith River, in a sandstone, probably the 

 same as No. 1 of the section. 



Bulla scbcylindrica. 



Shell elongate oval, or subcylindrical ; spire umbilicate ; surface (of cast) 

 marked with faint remains of lines of growth, crossed by about forty revolving 

 stritE, generally a little narrower than the elevated spaces between. Aperture 

 very narrow, arcuate, extending a little above the summit of the body, and in- 

 creasing in breadth very gradually from the upper to the lower extremity. Um- 

 bilicus small or closed. Length -91 inch ; breadth -48 inch. Breadth of aper- 

 ture near the centre '12 inch ; breadth at the widest place below -24 inch. 



This species, of which we have seen only a cast, is near Bulla pupa of Evans 

 and Shumard, (unpublished MSS.,) but the form of the aperture is quite different, 

 being very narrow, almost linear, excepting at the lower end, where it widens 

 out gradually, on the inner side, to about twice its breadth near the middle, 

 while that of B.pupa is " elongate ovate." From our B. volvaria (Proceedings 

 of the Academy of March last, page 69,) it may be distinguished by its larger 

 size, and the equal breadth of the two ends ; it differs from all the other 

 ISiebraska species we have seen, in its greater size and much more elongate 

 form. 



Locality and position. Near mouth of Milk River, formation No. 4 of the ac- 

 companying section. 



Panop^a occidentalis. 



Shell elongate ovate ; posterior end broader than the anterior, subtruncate 

 and gaping ; buccal end narrowly rounded, almost closed ; base straight along 

 the middle, rounding up abruptly behind, and gradually in front; cardinal 

 border nearly parallel with the base behind the beaks, and sloping in front ; 

 beaks small, rather depressed, incurved, approximate and located a little in 

 advance of the center ; surface ornamented by irregular concentric wrinkles or 

 undulations, most distinct on the upper half. 



We have but one specimen of this species, which shows none of the internal 

 characters, and has lost its finer surface markings, if there were any, by the 

 exfoliation of the external lamina. It is too imperfect to give exact measure- 

 ments, though it must have been about 3-10 inches in length, 2 inches high, and 

 1-42 inches wide. We are in some doubt whether or not it is distinct from a 

 species described by Prof. Tuomy under the name of F. cretacea, (see Proceed- 

 ings of the Academy, Sept., 1854, page 170,) though it is much larger; and it 

 is hardly probable, had his species differed much in the breadth of the two ex- 



