20 



Figs. 13, 14, Plate XXIX, of that work. Subsequently, during 1869 and the 

 following years down to the present time, the Green River basin has been 

 sedulously explored by Professor O. C. Marsh with the most important and 

 fruitful results. In the abundance of fossils and the number of extinct genera 

 and species of vertebrates they represent, his collections are perhaps not 

 exceeded by any obtained from any one locality elsewhere in the world. 

 Professor Marsh has given a succinct account of the geology of the region in 

 the American Journal of Science for 1871, and in the succeeding volumes 

 brief descriptions of the many species and genera of extinct animals discov- 

 ered by him. 



In 1869 Professor Hayden, during his geological exploration of Wyoming, 

 also examined the Green River Tertiary formations, and designated the more 

 superficial ones under the name of the- Bridger group. The fossils collected 

 from the latter were submitted to the examination of the writer, and are 

 briefly noticed in the Proceedings of the Academy for 1870, and likewise in 

 Professor Hayden's reports of 1870 and 1871. 



During the same and the succeeding years down to the present time, Drs. 

 Carter and Corson explored the buttes in the vicinity of Fort Bridger and 

 discovered many important fossils. Their collections from time to time were 

 transmitted to the author, and by far the greater number of the animals char- 

 acterized in the following paper are indicated from the specimens of these 

 collections. Most of them have also been briefly noticed in the later volumes 

 of the Proceedings of the Academy, and in Professor Hayden's reports for 

 1870 and 1871. 



I may further remark that during the last summer Professor Cope made 

 an extended exploration of the Green River basin, and obtained large collec- 

 tions of fossils, to a full account of which we look forward with much interest. 



Fig. 14. Perforated elk-tusk; one of a number of similar specimens found together with a "teshoa" 

 and human hones which had fallen from an old Indian grave, at the edge of a butte, three miles from 

 Fort Bridger. 



