616 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



by comparing the two specimens. After studying the types of C. extenuatns 

 I can see no reason for referring to it this coarsely sculptured form, which 

 also differs in outline. As has already been stated, the types of C. extenuatus 

 are unrecognizable casts in sandstone, showing neither the sculpture nor 

 the form of the ears. It is probably either C. bellistriatus or C. pertenuistri- 

 atus, and in consideration of this doubt I prefer to use the later name, C. 

 pertenuistriatus, because it is better characterized. 



The figured specimens of C. platessiformis above referred to came from 

 the south base of Aquarius Plateau, southern Utah, and east of Belle 

 Fourche River, near Bear Lodge, Black Hills. Those in the present collec- 

 tion were obtained near the head of southeastern valley of Fan Creek; 

 north side of Fan Creek Pass; top of hill 3 miles southeast of Gravel Peak, 

 and near the lower canyon of the Yellowstone. 



AviCULA (OxVTOMa) WYOMINGENS1S 11. Sp. 



Pteria {Orytoma) muiisteri (Broun) Meek and Hayden, 1865: Pala?oiit. Upper 



Missouri, p. 80, figs. a-b. 

 Pteria or Avicula mucronata Meek and Hayden, 1865: Ibid., p. 81, suggested name for 



the species in case it proves distinct. 

 Avicula (Oxytoma) mucronata (M. and H.) Whitfield, 1880: Geol. Black Hills Dakota, 



p. 357, PI. IV, figs. 1, 2. 

 Not Oxytoma mucronata (Meek) Wkiteaves, 1884: Geol. Surv. Canada, Mes. Foss., 



Vol. I, pp. 238 and 251, PI. XXXI, fig. 9, PI. XXXIII, fig. 6. 

 Not Avicula mucronata Gabb, 1864: Palreont. California, Vol. I, p. 30, PI. V, fig. 27. 



A new name is proposed for this fairly well known species for the fol- 

 lowing reasons. In Meek and Hayden's original work it was provisionally 

 referred to A. mwnsteri, with the statement that it would probably prove to 

 be distinct, and if so it should be named Pteria mucronata. A comparison 

 with figures of A. mwnsteri shows that they are not identical in either form 

 or sculpture, and later authors have recognized the American fossil as a 

 distinct species under Meek and Hayden's suggested name. This name 

 can not be used for it, however, because it was previously applied by Gabb 

 to an entirely different species from the Triassic of California. 



The fossil from the Lower Cretaceous of Queen Charlotte Islands 

 referred to this species by Whiteaves seems to me to be specifically distinct. 



The collections from the Yellowstone National Park contain only two 

 small immature specimens from the foothills at the base of north slope of 



