INVERTEBRATE PALEONTOLOGY. 315 



which defect gives a somewhat unnatural appearance to that part of (lie 

 figure. 



Lunatia obliquata (= Natica obliquata, Hall and Meek), is also a very 

 closely allied type, so much so, indeed, that I have sometimes suspected that 

 both the original E. concinna, and the shell here ranged under that name, should 

 be regarded as belonging to that species. In one character, however, E. 

 obliquata seems to present a rather marked and important. difference ; that is, 

 in having a well-defined opercular groove along the columella, not seen in 

 the original E. concinna, nor any of the well-preserved specimens here referred 

 to the same. 



Mr. Grabb cites E. rectilabrum (= Nalica rectildbrum, Conrad) as a 

 synonym of Natica concinna, Hall and Meek; but if the presence of the 

 opercular groove is a specific character, Mr. Conrad's species would seem 

 more properly to be a synonym of N obliquata, Hall and Meek. At any 

 rate, some good specimens before me from Alabama, belonging to the Smith- 

 sonian Museum, labeled N. rectilabrum, Conrad, by Mr. Grabb, and agreeing 

 nearly in form and general appearance with both N. obliquata and N. concinna, 

 Hall and Meek, show the opercular groove of the former well defined. Of 

 course, if the name Euspira should ultimately be made to replace Lunatia 

 for this genus, the name of this shell will have to be written Euspira con- 

 cinna. 



Locality and position. — The original typical specimen of L. concinna was 

 found on Sage Creek, Dakota, in the higher beds of the Fort Pierre group of 

 the Upper Missouri Cretaceous series. Those now before me are from the 

 Fox Hills group of the same series, on Moreau River, in Dakota Territory. 

 Dr. Hayden has also found imperfect specimens, believed to belong to the 

 same species, near the eastern base of the Rocky Mountains, seven to ten 

 miles west of Greeley, Colorado. 



1, ii ii a J i si occuden talis, M. & H. 



Plato 32, figs. 12, a, b, e. 



Natica ocddentalis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci.Philad., VIII, 64. 

 Natica (Lunatia) occidcntalis, Meek and Hayden (I860), ib., XII, 422. 



lunatia ocddentalis, Gablj (1861), Syuop. Moll. Cret. Form., 58.— Meek (1864), Smithsonian Check-List N. 

 Am. Cret. Fossils, 21. 



Shell obliquely ovate ; spire rather elevated ; volutions four and a half 

 to five, convex, and separated by a very distinctly-defined suture ; surface 

 marked by fine lines of* growth, crossed by numerous, very fine, obscure, 

 minutely flexuous, revolving striae ; aperture obliquely ovate, nearly straight 



