634 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



the Colorado formation on ridge north of north head of Gardiner and on 

 north side of Fan Creek. 



Inoceramus umbonatus Meek and Hayden. 



Inoceramus umlonatm Meek and Hayden, 1858: Proc. Acad. Nat. Sci. Plnla., p. 50. 

 Meek, 1876 : U. S. Geol. Surv. Terr., Vol. IX, p. 44, PI. Ill, figs, la, b, c; PI. 

 IV, figs, la, b and 2a, b. Stanton, 1894: Bull. U. S. Geol. Surv. No. 106, p. 81, 

 PI. XVIII, figs. 1 and 2. 



One specimen was collected on north bank of Snake River one-fourth 



mile above the mouth of Sickle Creek. The species is abundant in the 



shales of the upper part of the Colorado formation on the Missouri River 



below Fort Benton, Montana, and it has recently been collected by Mr. 



C K. Gilbert in the Niobrara shales near Rocky Ford on the Arkansas 



River below Pueblo, Colorado. It also occurs in the Austin limestone 



of Texas. 



Inoceramus undabundus Meek and Hayden. 



Inoceramus undabundus Meek and Hayden, 1S62: Proc. Acad. Nat. Sci. Phila., p. 26. 

 Meek, 1876 : U. S. Geol. Surv. Terr., Vol. IX, p. 60, PI. Ill, figs. 2a, b. Stanton, 

 1894: Bull. U. S. Geol. Surv. No. 106, p. 84, PI. XVI, figs. 1 and 2. 



Occurs with the preceding at the locality on Snake River, and also on 

 the Missouri below Fort Benton. 



Inoceramus flaccidus White. 



Inoceramus flaccidus White, 1876: U. S. Geog. and Geol. Surv. W. 100th Meridian, 

 Vol. IV, p. 17S, PI. XVI, figs. 1« aud b. Stauton, 1894: Bull. U. S. Geol. Surv. 

 No. 106, p. 80, PI. XIII, fig. 1. 



Occurs with the preceding, and at the same horizon, one-fourth mile 

 farther up Snake River. It has hitherto been found only in the Niobrara 

 shales near Pueblo, Colorado. 



Inoceramus acuteplicatus n. sp. 

 PI. LXXV, figs. 9 and 10, aud PI. LXXVI, fig. 1. 



Shell large, moderately convex, elongate, with the height much greater 

 than the length; hinge line rather short, oblique to the longer axis of the 

 shell; beak prominent, acute, near the anterior end of the hinge line; 

 anterior side gently convex, posterior nearly straight ; base broadly rounded, 

 with a tendency to angulation at the junction with the sides; surface marked 



