TO JUNCTION OF GRAND AND GREEN RIVERS. 129 



90°; surface ornamented by about thirty small, simple, radiating costpe, all of which 

 appear to be continued to the beaks. 



Beight, <>.27 inch: breadth, 0.23 inch: convexity, 0.22 inch. 



1 here may be fine concentric markings on well-preserved specimens of this species, 

 though none are visible on that from which the above description is made out. The 

 radiating costse are small, regular, and about equal to the grooves between. They 

 are moderately well defined, but seem to become gradually obsolete toward the anterior 

 and posterior dorsal margins. It is a neat little shell, presenting a regular cordate out- 

 line ;is seen from the anterior or posterior side. 



Locality cmd position. — Riodela Plata; base of upper member of the New Mexican 

 ( fretaceous series. 



GASTEROPODA. 



Genus ACTJEON, Montft, 

 Action intercalaris, Meek. 



Plato II, figs. 4 a, b, c. 



Shell small, narrow-subovate, or subfusiform; spire rather elevated; volutions five 

 to five and a half, compressed-convex, increasing gradually in breadth, and more 

 rapidly in height; last one a little produced below, and forming about half the entire 

 length; suture well defined; aperture narrow-subovate, very acutely angular above; 

 surface marked by fine, slightly-impressed, punctured stria', about twelve of which may 

 be counted on the second turn. 



Length, about 0.40 inch: breadth, 0.21 inch; apical angle nearly regular or a little 

 convex, divergence about 35°. 



The only specimen of this species in the collection has the lower part of the aper- 

 ture and a portion of the columella broken away. The aperture, however, was evi- 

 dently quite narrow, and the columella somewhat tortuous, with apparently one oblique 

 fold below the middle. The line, punctate, revolving grooves are not more than from 

 one-third to one-half as wide as the spaces between on the second whorl, and can 

 scarcely be seen without the aid of a magnifier. 



This shell is more nearly allied to A. subelliptica (Meek and Ilayden), from the 

 Fort Pierre Group (—Cretaceous formation No. 4) of the Upper Missouri section, 

 than any other with which I am acquainted. It may be readily distinguished from 

 that species, however, by the much greater elevation of its spire in proportion to the 

 length of its bodv-whorl, being in this respect about intermediate between A. suhelliptica 

 and A. attmuata (M. & II.), but quite distinct from them both. 



Locality and position. — Same as last. 



Genus ANCHUEA, Conrad. 

 Anchura ? Newberryi, Meek. 



Plato II, fig. ."). 



Shell of medium size, thin, fusiform; spire moderately elevated; volutions six, dis- 

 tinctly convex, increasing rather rapidly in size; suture well defined. Surface orna- 

 17 s F 



