UNDOUBTED TERTIARY SPECIES. 195 



Locality and ^position. — Ham's Fork, near Fort Bridger, Wyoming Ter- 

 ritory, from the Bridger group Tertiary ; Colonel Simpson's collections, in 

 the Museum of the Smithsonian Institution. 



MELANIIDJE. 



I 



Genus MELANIA, Auct. 

 Melania ? scuLPTiLis, Meek. 



Plate 17, fig. 8. 



Melania {Goniobasis ?) sculptilis, Meek (1870), Proceed. Acad. Nat. Sci. Philad., 58. 

 Compare Melania Taylori, Gabb (1869), Palseont. Oaliforuia, II, 13, pi. 2, fig. 21. 



Shell of medium size, conoid-subovate ; spire more or less elongate- 

 conical, with convex slopes, the apical angle being greater in the young 

 than in the adult, not eroded at the apex ; volutions six to seven, rather dis- 

 tinctly convex ; suture strongly channeled ; aperture ovate, a little oblique, 

 rather narrowly rounded below; lip sharp, most prominent below the 

 middle, and slightly sinuous at the lower inner side. Surface elegantly 

 ornamented by numerous, very regularly disposed, slightly flexuous or sig- 

 moid, vertical costse,* which are crossed by equally distinct and regular 

 spiral ridges, about four of which may be counted on each volution of the 

 spire (excepting those near the apex, which are smooth), and eight to ten 

 on the last turn, on the under half of which they are most strongly defined ; 

 minute lines of growth may also be seen by the aid of a magnifier ; costse 

 slightly nodulous at the points where they are crossed by the little revolv- 

 ing ridges. 



Length, 0.62 inch; breadth, 0.27 inch. 



This is a neat species, remarkable for its sharply-defined and very regular 

 cancellated style of sculpturing. The vertical costse are equally well defined 

 on all the volutions, excepting those near the apex, and on the under side 

 of the last one ; while the revolving lines, or ridges, become a little more 

 distinct on the lower part of the body-turn. Although there are nearly 

 always four of these revolving ridges on the volutions above the last one, 

 in a few examples as many as six may be counted on these turns ; but this 

 is due to the intercalation of a smaller one between two of the others, and 



* These are represented too straight on the figure. 



