428 GEOLOGY OF THE BLACK HILLS. 



Genus ANCHURA Conrad. 

 ANCHUBA ? SUBLEVIS. 



Plate 12, fig. 6. 



Aporrhais sublevis M. & H., Proc. Acad. Nat. Sci. Phil., vol. 12, p. 178. 



Aporrhais sublevata (misprint) M. & H., ibid., 1860, p. 428. 



Anchura f sublevis Meek, Smithsonian Check List Invert. Foss., p. 19. 



Anchura f sublevis (M. & H.) Meek, Pal. TJ. S. Geol. Surv. Terr., p. 327, PI. 19, fig. 3. 



Shell small, with an elevated, slender spire ; volutions about seven in 

 number, distinctly convex, with well-marked suture lines ; body volution a 

 little more ventricose than the preceding, very slightly angular, and ex- 

 tended below into a slender, pointed, rostral beak ; lip not expanded, but 

 the margin making a strongly sigmoidal curve, being broadly sinuate above 

 and extended forward below the middle, again receding to the beak. Volu- 

 tions marked by numerous fine, sigmoidally-curved, vertical folds, having 

 the same direction as the margin of the aperture, and also by fine, closely- 

 arranged, thread-like, and elevated revolving lines. Aperture obliquety 

 ovate, pointed above and below. 



On some specimens we notice a tendency in the vertical folds to form 

 varices on opposite sides of the shell, similar to those of Triton and Ranella; 

 mostly confined to the two larger volutions, and we strongly suspect that 

 the true generic relations of the shell have not been properly ascertained ; 

 also that the specimen in hand, although quite numerous, as also those used 

 and figured by Mr. Meek, are all young shells, with the adult features of 

 the aperture yet undeveloped. 



Formation and locality. — In limestone of the Fort Pierre" Group, near 

 Box Elder Creek, Black Hills, Dakota 



