TO JUNCTION OP GRAND AND GREEN RIVERS. 129 



90; surface ornamented by about thirty small, simple, radiating costa?, all of which 

 appear to be continued to the beaks. 



Height, 0.27 inch; breadth, 0.23 inch; convexity, 0.22 inch. 



There 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 costge are small, regular, and about equal to the grooves between. They 

 are moderately well denned, 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 as seen from the anterior or posterior side. 



Locality and position. Rio de la Plata; base of upper member of the New Mexican 

 Cretaceous series. 



GASTEROPODA. 

 Genus ACTION, Montft. 



ACTJEON INTERCALARIS, Meek. 

 Plate 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 striae, 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 fine, 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 Hayden), 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 body-whorl, being in this respect about intermediate between A. subelliptica 

 and A. attenuata (M. & H.), but quite distinct from them both. 



Locality and position. Same as last. 



Genus ANCHURA, Conrad. 

 ANCHURA ? NEWBERRYI, Meek. 



Plate II, fig. 5. 



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 



