white.] PALEONTOLOGY CEETACEOUS FOSSILS. 303 



Position and locality. — Strata of Cretaceous age, probably of the Fox 

 Hills Group ; Monument Creek, near Colorado Springs, where it was col- 

 lected by Mr. TV. H. Holmes. 



Genus ANISOMYON Meek & Hayden. 

 Anisomyon centrale Meek. 



Plate 9, figs. 1 a, i, c, and d. 



Anisomyon centrdle Meek, 1872, An. Rep. U. S. Geol. Surv. Terr, for 1870, p. 312. 

 Anisomyon centrale White, 1876, U. S. Expl. and Surv. West 100th Merid., p. 194, pi. 

 xviii, f. 8. 



" Shell depressed conical, somewhat wider than high ; apex central, or 

 very nearly so ; slopes nearly equal all around, or with sometimes the 

 anterior and sometimes the posterior side a little convex, and the others 

 more nearly straight; aperture circular; surface apparently smooth, 

 excepting obscure lines of growth, crossed by several irregular, diverg- 

 ing, obscure, radiating ridges, and more strongly defined furrows ; the 

 former being mainly on the posterior and the latter on the interior 

 [anterior ?] and lateral slopes. 



"Breadth of largest specimen seen, 1.16 inches; height, about 0.95 

 inch. 



"I have seen only two specimens of this species, and these are 

 internal casts, with merely some fragments of the very thin shell remain- 

 ing, while the extreme apex of both is broken away. The radiating fur- 

 rows are rather distinctly defined on the anterior slope of the internal 

 cast, while one (not apparently the middle one) is narrower and dis- 

 tinctly deeper than the others on each side of it, which latter are about 

 twice as wide, shallow, and often somewhat divided by a small ridge 

 down the center of each. On the posterior slope, one of the ridges is 

 more strongly defined than the others, especially near the apex, and 

 seems to correspond to the deeper furrows of the anterior slope, though 

 not exactly opposite to it. The broken apex in one of the specimens 

 looks as if it might have been curved a liitle backward, though in the 

 other it evidently curved forward at the point, if I have rightly de- 

 termined the relative sides. One of the specimens shows obscure traces 

 of the oval muscular scar on each side, and these are connected across 

 the side I regard as the anterior by a slender line, but the specimen 

 being a little worn on the opposite or posterior side, I have been unable 

 to make out the broader interrupted band that ought to pass around the 

 posterior side if the species really belongs to this genus. 



" This species will be readily distinguished from all of the others yet 

 known from the far Western Cretaceous rocks by its conical form and 

 elevated apex. 



"Locality and position.— Box Elder and Colorado City, Colo.; Fox 

 Hills Group of the Upper Missouri Cretaceous series." 



The illustrations of this species on plate 9 were prepared by Mr. Meek 

 a short time before his death. The specimens were collected by Mr. TV. 

 H. Holmes, and other specimens of the species have been discovered on 

 Gallinas Creek, New Mexico, by Professor Cope, and published by the 

 writer (loc. tit.). These are merely casts in indurated clay, and do not 

 therefore correctly represent the natural proportions of the shell, because 

 their height had been much reduced by vertical pressure. Still later, 

 a few others were discovered by the writer west of the Eocky Mountains 

 in Northwestern Colorado. 



