3Iesozoic and Ccenozoic Geology and P^alceontology. 193 



Jlaccidus, Mactra incowpta; from the Rio Puerco, New Mexico, Ido- 

 nearca depressa; from Mount Taylor, New Mexico, Lispodesthes lin- 

 fjulifera; from Ojo de los Ciiervas, New Mexico, Ammonites laevianus; 

 from Paria, Utah, Ilelicoceras pariense^ and Serpmla intrica. 



Prof. E. D. Cope* described, from the Fort Pierre Group of Kansas, 

 Pelycorapis herycinus; and from the Niobrara Group of the Upper 

 Missouri, Elasmosaurus serpentinus^ and Anogmius aratus. 



Prof. O.C. Marshf described, from West \s.Si\-\?,2i^^ Baptornis advenus; 

 from Texas, Graculavus lentus^ Diplosaurus felix; from the Rocky 

 Mountain region, JVanosaicrus agilis^ N. victor^ Apatodon mirus ; and 

 from the Dakota Group of Colorado, Titanosaurus niontayius. 



In 1878, Prof. C. A. WhiteJ; surveyed a portion of Northwestern 

 Colorado, and found the Dakota Group reaching an aggregate thick- 

 ness of between 500 and 600 feet; the lower half consisting of a dark- 

 colored, coarse, silicious, pebble-conglomerate, which is somewhat 

 irregularly bedded and easily disintegrated; and the upper portion, 

 consisting of a yellowish or brownish, rough, heavj-bedded sandstone, 

 between which and the conglomerate some variegated bad-land sand- 

 stones usually exist. 



The equivalent of the Fort Benton and 'Niobrara Groups he called 

 the Colorado Group, which is also the equivalent of the Sulphur Creek 

 Group. He united, under the name of the Fox Hills Group, both the 

 Fox Hills and Fort Pierre Groups, the former of which has a thickness 

 of 1,000 feet, and the latter of 800 feet. The strata that have been 

 called by the name of the Fort Union Group, Lignitic Group, Bitter 

 Creek Group, Judith Ris^er Group, and by other names, including the 

 name of Laramie Group, proposed b}^ Mr. King, he proposed to call 

 Post-Cretaceous, The thickness of this group in Northwestern Colo- 

 rado is at least 3,500 feet. 



He described, from the Laramie Group,§ on Crow creek and Danforth 

 Hills, in Northern Colorado, Volsella 7'egidaris. V. laticostata, N'ucu- 

 lana inclara, Anodonta parallela^ Corhicula clehumi^ C. cnrdinice- 

 formis, C. obesa, C. macropistha^ Physa felix, Viviparus prudentia, 

 Odontobasis formosa\ from Black Buttes Station, Wyoming, TJnio 

 ■goniambonatus, U. aldrichi, Neritinabaptista; from Bear river, near 

 the confluence of Sulphur creek, W^'oming, Acella lialdemani, Nevi- 



* Bull. U. S. Geo. Sxir., Vol. 3, Xo. 3. 

 t Am. Jour. Sci. and Arts, 3d Ser., Vol. U. 

 X 10th Rep. Hayden's U. S. Geo. Sur. Terr. 

 g Bull. U. S. Geo. Sur., Vol. 4, No. 3. 



