white. J PALEONTOLOGY — CRETACEOUS FOSSILS. 275 



Position and locality. — Strata, probably equivalent with, the Fort Pierre 

 and Fox Hills Groups of the Upper Missouri, at Cimarron, 1ST. Mex., where 

 it was discovered by Prof. O. H. St. John, in whose honor the specific 

 name is given. These strata are discussed by him in " Notes on the 

 Geology of Northeastern New Mexico," Bull. TJ. S. Geol. & Geog. Surv. 

 Terr. vol. ii, No. 4. 



CAEYOPHtXLlA EGEEIA (sp. nOV.) 

 Plate 6, figs. 7 a and 7 b. 



Corallum reversely conical or cupuliform ; sides more or less convex ; 

 base rounded ; calyx subcircular, shallow ; the border apparently a little 

 thickened and slightly projecting 5 septa about 30, each alternating one 

 not reaching the columella, their sides are marked vertically by small, 

 slightly-raised ridges, giving their edges a rugose appearance when 

 broken across transversely ; columella composed of loosely aggregated, 

 irregular, coarse threads. 



All the examples that were discovered are imbedded in rock, and none 

 of them show the outer surface satisfactorily, but the epitheca seems to 

 have been thin, and the vertical costse not prominent. 



Height about 7 millimeters ; diameter of the calyx the same ; but these 

 proportions vary, some of the examples being proportionally shorter. 



The condition of all the discovered examples of both this species and 

 C. joliannis is such as to render it difficult to satisfactorily ascertain 

 their true generic character, and it is not certain that one or both of 

 them ought not to be referred to TrocJiocyathus Edwards & Haime. 

 They, however, clearly belong to the family Caryophyllidw, and in view 

 of the exceeding rarity of any of the actinaria in the Cretaceous rocks 

 of North America, their discovery is of much interest. 



MOLLUSCA. 



CONCHIFERA. 



Genus OSTREA Linnseus. 



Ostrea quadeiplicata Shumard. 



Plate 5, fig. 6 a, and plate 8, figs. 3 a and 6. 



Ostrea quadriplicala Shumabd, 1860, Trans. Acad. Sci. St. Louis, vol. 1, p. 608. 



? Ostrea crenulo-margo Eoemee, 1852, Kreidebildung von Texas, p. 76, pi. is, f. 6a and 6 b. 



The following is Dr. Shumard's description of this species: "Shell 

 small, usually arcuate, rarely elongate-subovate, longer than wide; ante- 

 rior and basal margin's produced into four angles, which are sometimes 

 quite salient, and margin more or less deeply excavated. Superior valve 

 fiat, or a little convex at the umbo ; beak obtusely rounded or subtrun- 

 cate at tip; surface elegantly ornamented with imbricating lines of 

 growth, which are crossed by numerous radiating strise; margins finely 

 crenulate; interior gently concave; muscular impression subovate, situ- 

 ated near the anal border; ligament facet short, subtrigonal, and finely 

 striated transversely. Inferior valve more or less gibbous, posterior 

 slope falling abruptly to the margin; beak moderately sharp, rounded 

 at lip and directed upward and backward ; surface with imbricating 



