328 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



species it may be at once distinguished by its more convex whorls and much 

 coarser, as well as more distant, revolving lines. Its lines of growth are 

 also not near so flexuous in crossing the volutions of the spire as those of 

 A. biangulata. 



This and the following species are ranged provisionally in the genus 

 Anchura, and may belong to some other group, as we have seen no speci- 

 mens of either showing the form of the lip, or whether or not there was a 

 posterior canal. 



Locality and position. — Yellowstone River, 150 miles from its mouth ; 



in beds containing a mingling of the fossils of the Fort Pierre and Fox Hills 



groups. 



A ii «■ li ii r ;i ! p a r v a , M. & H. 



Plate 19, figs. 4, a, b. 



Aporrhuis parva, Meek and Hayden (1860), Proceed. Aead. Nat. Sci. Philad., XII, 178. 

 Anchural parva, Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 19. 



Shell very small, irregularly subfusiform ; spire moderately elevated, 

 and acute at the apex; volutions six or seven, separated by a small but 

 rather distinct suture, and having around the middle a single series of very 

 oblique, flexuous folds, or node-like costse, which do not extend to the suture 

 either above or below; last whorl rather large, and having, just below the 

 row of nodes, a small but well-defined revolving ridge; surface marked by 

 very obscure lines of growth, and fine, closely-set, revolving striae ; (beak and 

 lip unknown). 



Length, about 0.28 inch ; breadth of body-whorl, 0.15 inch. Apical 

 angle a little convex ; divergence, 33°. 



I have seen but one specimen of this little shell, which has the lip 

 broken away, and does not show the columella or the form of the aperture. 

 Consequently, it is only provisionally that it has been referred to the above 

 genus. It may be readily distinguished from all of the allied forms yet 

 known from these rocks, by its broader form, less attenuated spire, and pro- 

 portionally larger, more distant, and more oblique, flexuous, node-like folds 

 around the middle of the whorls. These folds, or nodes, are entirely 

 unlike the small vertical costse on any of the other species already described, 

 being so broad and distant that only about ten of them occupy the whole of 

 the body-whorl. 



Local Hi/ anil position,. — Same as last. 



