314 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



synonym of Ampullina; this latter genus differing from both the true Ampul- 

 Una and from the group to which they apply it, in having its columella not 

 only thickened, but flattened and dentate nearly as in Nerita, to which family 

 some refer it. 



Li u ii a t i a concinna, H. & M. (sp. ). 

 Plate 32, figs. 11, a, b, c. 



Tfatica concinna, Hall and Meek (1854), Ain. Acad. Arts and Sci., V, 384, pi. iii, figs. 2, a, b, c, d. — Gabb 



(1861), Synop. Moll. Cret. Form., CO. 

 Xailca Morcattensis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci., Philad., VIII, 64 ; and ib., 282. 

 Xatica (Lunatia) Moreauensis, Meek and Hayden (I860), ib., XII, 422. 

 Lunatia Moreauensis, Gabb (1861), Synop. Moll. Cret. Form., 58. — Meek (1864), Smithsonian Check-List N. 



Am. Cret. Fossils, 20. 

 Compare Natica obliquata, Hall and Meek (1854), Am. Acad. Arts and Sci., 3S4, pi. iii, figs. 1, a, b ; 



and A', recttldbrum, Conrad, Jour. Acad. Nat. Sci., Philad., IV (2d ser.), 344, pi. 58, fig.28. 



Shell oblicpiely rhombic-subovate, or subglobose ; spire moderate ; volu- 

 tions three and a half to four, convex, and separated by a deep suture ; last 

 one comparatively large ; surface marked by fine, rather obscure, lines of 

 growth, crossed by nearly obsolete, minutely flexuous, revolving striae, only 

 seen on well-preserved specimens ; aperture subovate, being straighter on 

 the inner than the outer side; umbilicus small, and sometimes showing a 

 slight tendency to develop a small revolving ridge within ; inner lip a little 

 thickened, and slightly reflected upon the body-volution above the umbilicus. 



Length of a mature, rather gibbous, specimen, 0.90 inch ; breadth of 

 same, 0.76 inch. 



This shell varies somewhat in form ; some individuals being proportion- 

 ally a little shorter, and having the body-volution more ventricose than others. 

 For a long time, it was believed to be distinct from N. concinna, and conse- 

 quently the name A r . Moreauensis was proposed for it. Since seeing a good 

 series of specimens, however, showing the form and general appearance of 

 the shell at various stages of growth, I am led to believe that it is not spe- 

 cifically distinct, from the type of N. concinna, which is now believed to be a 

 young individual. At any rate, small specimens now before me, of the same 

 size, seem to agree almost exactly with the type of iV. concinna ; while I am 

 at a loss to separate these specifically from the larger individuals, such as 

 those for which the name N. Moreauensis was proposed. 



It should be here more distinctly explained, however, that the inner lip 

 is represented too thin, and too straight on. its left margin, and not enough 

 reflected upon the body-volution above the umbilicus, in our figure 11, b ; 



