138 PEOCEEDINGS OP THE ACADEMY OP 



to about four distinctly elevated, revolving lines, which become ©bsolete near 

 the apex of the spire ; the upper of these lines is larger than the others, and 

 forms a well-marked keel, while the entire surface, above and below them, is 

 marked br smaller, irregular, revolving lines, which, with the lines of growth, 

 form a very fine indistinct cancellated style of ornament ; aperture oval ovate, 

 obtusely angular above ; outer lip rather sharp, prominent a little below the 

 middle, very faintly sinuous above; columella forming a gentle curve, scarcely 

 sinuate below, not perforate. Length '54 inch ; breadth -29 inch ; apical angle 

 convex, divergence variable with age, averaging about 45''. 



In some of its varieties this species approaches our M. Nebrascensis, (Proceed- 

 ings Acad. Nat. Sci. Phila.,vol. 8, p. 124,) but has much more convex volutions, 

 and greatly stronger revolving lines or keels, on the middle of the whorls. 



At the time we described M. Nebrascensis, we had but few specimens, and 

 those very imperfect; along with these there were one or two specimens of the 

 species now before us, which we were then inclined to regard as only a va- 

 riety of 31. Nebrascensis. The collection now in our possession shows, how- 

 ever, that they are distinct, consequently it will be necessary to modify some- 

 what our description of M. Nebrascensis, so as to include only those shells with 

 flattened or depressed convex whorls, and revolving lines, a few of which are 

 larger than others on the middle of the volutions, but never becoming distinct 

 angles or carinas. 



Locality and position. Fort Union, Lignite Tertiary formations. 



Melania convexa, (M. and H.) 



Proceedings of Acad. Nat. Sci. Fhila., Vol. 8, p. 125. 



From the same locality and position as the above, we find amongst some of 

 the late collections specimens presenting differences from that shell, which we 

 suspect may be of specific importance ; we are unwilling, however, without more 

 individuals for comparison, to run the risk of multiplying synonyms by attempt- 

 ing to characterize it as a distinct species. It is a more slender shell than 31. con- 

 vexa, the lower volutions are more rounded, and the suture much more dis- 

 tinctly impressed, especially between the lower whorls. For the present we will 

 designate this form as 3Ielania convexa, var. impressa, and in case further com- 

 parisons prove it to be a distinct species, it may be designated by the latter 

 name. 



Fusns Vaughani. 



Shell fusiform, rather thick ; volutions six to six and a half, convex, obliquely 

 a little flattened or concave above, last one narrowing somewhat abruptly below 

 into the (short?) canal ; ornamented by small regular vertical folds, which are 

 crossed by prominent revolving bands, less than the spaces between, so as to 

 give the surface a coarsely cancellated aspect; of these bands about four on the 

 body volution, and two on those of the spire are larger than the others, and 

 form indistinct nodes, where they cross the vertical folds. Below these four 

 larger bands on the body whorl, there are about five or six other smaller and 

 more oblique bands, which diminish in size from above; while on the upper 

 obliquely flattened, or concave part of the same whorls, as well as on those of 

 the spire, there are about four much smaller revolving bands or lines. Entire 

 .surface marked by distinct lines of growth, which are crossed by fine rather 

 obscure revolving striaj, so as to produce, independent of the larger ornaments 

 above mentioned, a fine reticulated style of marking. Aperture narrow ovate 

 or oval ; outer lip bevelled ; inner lip thin, folded upon the arcuate and tortuous 

 columella. Length about 1-43 inclies ; breadth -75 inch ; apical angle convex, 

 divergence about 54°. 



This species is quite unlike any of those we have hitherto seen from the Ne- 

 braska formations. Although apparently occurring in the same bed with avcII 

 m arked Cretaceous forms, it is, like many of the upper Cretaceous species already 

 described by us from this region, very nearly allied to forms belonging to the 



[May 



