MLSOZOIC FOSSILS. 611 



OsTBEA ENGELMANNI Meek. 



Ostrea engelmanni Meek, 18G0: Proc. Acad. Nat. Sci. Phila., p. 311. 1876: Simpson's 

 Kept. Expl. Great Basin, Utah, p. 355, PI. Ill, fig. 6. Meek and Hayden, 1865: 

 Paheont. Upper Missouri, p. 73, figs. A, B. White, 1884: Fourth Ann. Bept. 

 U. S. GeoL Surv., p. 289, PL XXXIV, figs. 3, 4. 



A few fragments and immature specimens of this species were obtained 

 near the head of drainage of northeast valley of Fan Creek and top of hill 

 3 miles southeast of Gravel Peak. 



Gryph.ea planoconvexa Whitfield. 



PI. LXXII, figs. 9 and 10. 



Grypliwa planoconvexa, Whitfield 1876: Ludlow's Bept. Becounaissance from Carroll, 

 Montana, to Yellowstone Park, p. 142, PI. II, figs. 9 and 10. 



Shell of medium size, subcircular in outline ; attached valve moderately 

 convex with rather prominent beak, and in most specimens with an obscure 

 shallow furrow which separates a rather broad triangular lobe from the 

 body of the shell; upper valve varying from nearly fiat to deeply concave; 

 surface marked only by lines of growth and irregular concentric undula- 

 tions. The cartilage pit is very broad and shallow. 



An average specimen measures 57 mm. in length, 50 mm. in height, 

 and 27 mm. in thickness of the two valves united. 



This form was mentioned by Meek 1 as "Gryphsea, a small species of 

 the form of G. dilatata." It also resembles some varieties of the Upper 

 Cretaceous G. vesicularis and Ostrea patina. Whitfield's type, from the 

 Bridger Mountains, Montana, is somewhat more convex than any of our 

 specimens, and the figure does not show any furrow or lobe, but I have no 

 doubt that it is the same variable species. 



The specimens figured are from near lower canyon of Yellowstone 

 River, collected by Dr. A. C. Peale, and ridge southwest of second crossing 

 of Snake River, collected by Mr. W. H. Weed. It was also obtained on 

 north slope of ridge north of Gray Mountain; on divide at head of Fawn 

 Creek; ridge west of south branch of headwaters of Gardiner, and near 

 Snake River 3 miles west of mouth of Coulter Creek. 



Aim. Rept. U. S. Geol. Surv. Terr, for 1872, p. 472. 



