INVERTEBRATE PALEONTOLOGY. 333 



below, with Ihe lower margin a little sinuated or notched and reflexed; inner 

 lip somewhat twisted and flattened ; outer lip thin and sinuate above the 



middle. 



This genus seems to lie to some extent intermediate, in the characters 

 of its shell, between TurriteUa, Lamarck, and Troto, Defrance. It is, how- 

 ever, generally proportionally shorter, with volutions more rapidly increasing 

 in size than is common in TurriteUa ; from which it also differs in having its 

 aperture produced, with a sinuated margin anteriorly. From Prota it xliffers 

 in not having the anterior margin of its aperture near so strongly notched, 

 as well as in having its body-volution rounded below, and proportionally 

 larger, and its outer lip sinuous above. 



This genus probably commenced its existence during the Cretaceous 

 epoch. It certainly occurs in the Tertiary, and is represented by some six 

 to eight or more existing species. 



IScsalial Kansasensis, Meek. 



Plate 2, figs. 7, a, b. 

 TurriteUa /uiHsnsfnsis, Meek (1871), Haytleu's Report Geological Survey of the Territories, 312. 



Shell elongate-conical, or gradually and regularly tapering from below 

 to the apex, with the lateral slopes of the spire straight; volutions eight to 

 ten, increasing regularly in size, flattened, or only very slightly convex ; last 

 one rounded below; suture nearly linear; aperture ovate; surface with 

 small, thread-like, revolving lines, varying much in their arrangement and 

 distinctness, but usually more strongly defined on the lower half of the last 

 turn ; lines of growth very fine, obscure, and strongly arched or sigmoid, so 

 as to indicate a deep sinuosity in the outer lip above the middle. 



Length of a large specimen, 1.10 inches; breadth, 0.34 inch; divergence 

 of slopes of the spire, about 22°. 



This shell varies much in its surface-markings; some of the specimens 

 appearing almost smooth, or only showing faint indications of a few revolving 

 lines, while others show a few distantly-separated, very slender, raised lines. 

 In still others, five or six well-defined slender lines may be seen on' some of 

 the volutions, and a smaller number of less distinctly-defined ones on the other 

 turns. The arrangement of these lines and their comparative size on differ- 

 ent individuals, as well as on different parts of the same specimen, vary 

 much. Usually, the upper turns near Ihe apex of the spire appear to be 



