STANTON.] 



OSTREID.E. 63 



The fossils from Colorado above described seem to agree in every 

 respect with many of the published figures of the common European 

 species that is usually described under the name of Ostrea or Exogyra 

 columba. The differences are certainly not greater than those shown 

 by some of the forms referred to the species by European authors. 

 The species is known to have a wide geographic distribution, occurring 

 throughout Europe and in southern India in the Middle Cretaceous 

 (Cenomanian and Turonian). It is said to be best developed in the 

 zone with Inoceramus labiatus. With these facts before us it ought not 

 to be surprising to find the species associated with a similar fauna in 

 this country. On the contrary, it is strange that it has so long escaped 

 observation here. 



Exogyra columbella Meek may prove to be only the young or a vari- 

 ety of this species, but the two forms have not yet been found associ- 

 ated at the same localities, and it is thought best to treat them sep- 

 arately for the present. 



Locality and position. — In the Pugnellus sandstone near Malachite 

 post-office and Poison canyon, in Huerfano park, and at about the 

 same horizon at Rattlesnake butte and on the Arkansas river ; 20 miles 

 above Pueblo, Colo. 



EXOGYRA COLUMBELLA Meek. 



PI. vni, Figs. 2, 3, and 4. 



Exogyra costata, var. fluminis White, 187£, U. S. Geog. & Geol. Sur. West lOOtli 



Meridian, vol. iv, p. 174, PI. 17, Figs. Sa-d. 

 Exoyyra columbella Meek, 1876, Macomb's Expl. Exped. from Santa F6 to junction of 



Grand and Green rivers, p. 124, PI. I, Figs. 3a-d; White, 1884, 4th Ann. Rept. 



U. S. Geol. Sur., p. 304, PI. 55, Figs. 5 and 6. 



Prof. Meek's description and comments are as follows : 



" Shell small, rather thin, ovate; i>osterior side forming a semioval 

 curve from the umbo to the ventral edge; anterior side rounded below 

 the beak; ventral margin rounded. Lower valve convex, the most 

 gibbous part sometimes forming an obtuse umbonal 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 costse, which bifurcate along the umbonal 

 ridge; marks of growth rather obscure. % Upper valve flat, oval, appar- 

 ently smooth, or only having obscure lines of growth. 



" Length from the most prominent part ef the umbo to the ventral 

 margin, 1 inch; transverse breadth, 0.72 inch; depth or convexity, 

 about 0.42 inch. 



"It is possible that this shell may be identical with E. Icevitiscula of 

 Eoemer, 1 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 



i Kreid. von Texas, PI. IX, Fig. 3a, 6, c, 



