Academy of Science. 4S 



vicinity, if not upon the actual town-sites, of thriving villages, and foi* years numer- 

 ous fragments have been collected by tourists, and exhibited as specimens of pet- 

 rified wood! The abundance and wide extent of their remains is almost incredible. 

 The quantities hitherto obtained, although apparently so vast, are wholly unimpor- 

 tant in comparison with those jet awaiting the researches of geologists, through- 

 out the entire Rocky Mountain region ; I doubt not that many hundreds of tons 

 will eventually be exhumed. 



To an English geologist. Prof. Arthur Lakes, of Golden, Colorado, credit is due 

 for first detecting the osseous character, and appreciating the scientific value, of 

 these fossils. While engaged one day, in March, 1877, in company with Engineer 

 E. L. Berthoud, of Colorado, in collecting Dakota leaves from the summit of the 

 ridge, or " Hog-back," near Morrison, he discovered a huge caudal vertebra in bas- 

 relief upon a slab of sandstone. Upon further investigation, a large quantity of 

 bones were collected and shipped to Prof. Marsh, of Yale College, by whom they 

 were described under the name of Titanosavrus montanus. 



Almost contemporaneously with this discovery, the fossils were made known at 

 Canyon City, Colorado, by Mr. O. Lucas, a school teacher, and in Southern Wyo- 

 ming by Mr. Wm. Reed, an intelligent section foreman of the Union Pacific Rail- 

 road. Specimens from the former locality were sent to Prof. Cope, of Philadel- 

 phia, by whom they were named Camerasaurns supremi/s. Since then numerous 

 other localities have become known in Colorado and Wyoming, and I doubt not 

 but that future explorations will bring to light scores of outcrops rich in these ver- 

 tebrate remains. 



The beds consist of argillaceous shales of a grayish, or bluish gray color, 

 variously interspersed with sandy, or sandstone strata, of from four to six hundred 

 feet in thickness, the fossils extending through at least 300 feet in a vertical alti- 

 tude. At Canyon City the deposits lie immediately upon the characteristic red 

 sandstones of the Trias, the fossils having been detected to within seventy-five 

 feet of the conglomerate. The beds are apparently conformable, as shown by 

 the erosion of the valleys of two small streams, lying in a synclinal basin, the ridges 

 of which are convergent, thus giving a transverse strike to the uneroded strata 

 between the valleys. 



Skirting the eastern flanks of the foothills, and extending for several hundred 

 miles through Colorado and Wyoming, is a prominent ridge, or " Hog-back," of 

 several hundred feet in height, dipping often at an angle of from 40 to 60 degrees, 

 and usually protected above by the hard leaf-bearing sandstone of the Dakota 

 cretaceous. Along the western slope of this ridge the fossiliferous clays or sand- 

 stones are usually concealed beneath the debris washed over them, but whenever 

 exposed, as is often the case on the sides of valleys cutting through the Hog-back, 

 fragments of dinosaur bones may generally be detected. Such is the case at 

 Morrison, near Denver, where large quantities have been collected for the museum 

 of Yale College. The fossils here extend to within at least 200 feet of the well- 

 defined Dakota sandstone. Here, however, below the beds, the marine deposits 

 of the Jurassic are prominent, and all, together with the red Triassic, lying con- 

 formably upon the carboniferous. 



The stratigraphy is most characteristically shown at Como in Southern Wy- 

 oming. The summit of an anticlinal ridge has here been excavated, and a 

 basin formed for an alkaline lake. A steeply inclined ridge of several miles in 

 length is prominent immediately south of the lake with the fossiliferous strata 

 largely exposed. The fossil outcrops here extend from near the summit of harder 

 sandstone, which has not yet produced any cretaceous fossil leaves, down to near 



