TO JUNCTION OF GliAND AND GKEEN 1UVERS. 125 



rounded. Lower valve convex, tlie most gibbous part sometimes forming an obtuse 

 unibonal prominence, which is not separated from the front by a sulcus; beak slender, 

 pointed, and distinctly coiled to the left; surface ornamented by small, but distinct, 

 rather regular, radiating eost;y, which bifurcate along the umbonal ridge; marks of 

 growth rather obscure. Upper valve flat, oval, apparently smooth or only having ob- 

 scure lines of growth. 



Length from the most prominent part of the umbo to the ventral margin, 1 inch; 

 transverse breadth, 0.72 inch; depth or convexity, about 0.42 inch. 



Itis possible that this shell may be identical withjE. ^mzfscwfa of Roomer (Kreid. von 

 Texas, plate ix, fig. 3 a, &, e); but with the means of comparison now within my reach, 

 I can but regard it as distinct. All the specimens of it that I have yet seen are more 

 oval in form and have a less distinctly spiral beak than the form described by Roemer. 

 They also differ in having the under valve always marked by regular radiating costas, 

 while that of E. Icviuscula is generally quite smooth, or rarely presents traces of nearly 

 obsolete, rather broad, plications, as represented by fig. 3 c of Roomer's plate ix 

 (Kreid. von Texas). It seems likewise to be a thinner and less robust shell than 

 Roomer's species, and holds a lower stratigraphies! position. In surface-markings as 

 well as in general form, it closely resembles young specimens of E. colunila of Lamarck 

 (. \niin. sans Vert., vi, 108) as figured by Goldfuss in his Petrefact. Germ, and by 

 d'Orbigny in the Paleont. Francais. It never attains more than one-eighth the size of 

 adult individuals of that species, however, and differs in having an oval instead of a 

 circular upper valve. 



Locality and position. Covero, Lower Cretaceous; also at Sierra Abajo,from the 

 base of Middle Cretaceous, and at Galisteo, from the same member of Dr. Newberry's 

 section. 



Genus ANOMIA, Linn. 



ANOMIA NITIDA, Meek. 



I'latol, figs..4a,ft. 



Upper valve subcircular or a little oval transversely, very thin and brilliantly 

 pearly, depressed-convex, the most prominent part being near the middle; lateral mar- 

 gins nearly equally rounded, ventral border forming a semi-oval curve; cardinal mar- 

 gin arched, or apparently presenting a similar outline to the ventral side ; beak small, 

 much compressed, nearly or quite marginal, and located at the middle of the dorsal 

 side; surface marked by fine, rather regular, obscure, concentric striae. (Under valve 

 unknown.) 



Transverse diameter, 1.07 inches; diameter from the cardinal to the ventral mar- 

 gin, 0.89 inch. 



It is possible that some of the species referred to the genus Anomia from the Cre- 

 taceous and older rocks would be found to present fundamental differences from the 

 typical forms of this group if we could see the under valve and the hinge and muscu- 

 lar impressions. Some six or seven species are now known from the Cretaceous rocks 

 of this country, of nearly all of which, I believe, only upper valves have been found. 



Locality and position. Pope's Well ; top of Middle Cretaceous. 



