244 GEOLOGY OF THE DENVER BASIN. 



where the above fossils were found to Bijou Basin, at the head of the creek, 



Dr. White was unable to find any other fossil-bearing horizon, and but few 



outcrops of strata were seen north of the Kansas Pacific Railroad crossing. 



In Monograph II of the Harden survey, Prof. E. 1 >. Cope described 



two (linosaurian fossils from Colorado under the names Polyonax mortuarius 

 and Cionodon arctatus. These forms are now regarded by ( 'ope 1 as belong- 

 ing to the ( leratopsidse, Polyonax corresponding to Triceratops Marsh, while 

 the position of Cionodon. which is known only from teeth, is not certainly 

 established. Marsh also considers Polyonax to he a horned dinosaur, though 

 not surely separable from Agathaumas Cope. With the above forms occurs 

 a Hadrosaurus, and the turtles Compsemys and Trionvx. So far as the 

 Writer is aware, Professor Cope has not given the localities of these fossils 

 in connection with descriptions of theni^ hut on personal inquiry he kindly 

 stated that they were obtained on Bijou ('reek, about 40 miles east of 

 Denver, but he could not specify the exact locality. 



'The locality of Bijou (/reek is interesting, as its general position in 

 certain important particulars is much like that of the Converse County, 

 VVvo.. locality, and that of the Judith River Basin in Montana. In all 

 these cases the beds lie some distance away from the main mountain range, 

 and the connection with the more complete sections commonly found in 

 the foothill region is interrupted. As in Wyoming and Montana, so in 

 Bijou Valley, the first natural assumption of the collector would he that 

 the strata containing the vertebrates belonged to the Laramie. But as the 

 Laramie of the Colorado foothills is not known to contain these or allied 

 remains while the Arapahoe beds do contain them, and as the latter, in all 

 probability, once extended much farther out into the plains area than the 

 eastern boundary of the Denver map. it seems strongly probable that 

 the dinosaurs described hv Professor Cope came from Arapahoe beds 

 reappearing from beneath Denver and Monument ('reek sediments in the 

 valley of Bijou < 'reek. 



CONCLUSIONS FROM EVIDENCE. 

 Individuality of formations established. The'factS of Stratigraphy alld Hthology 



seem to the writer much more than sufficient to prove that the Arapahoe 



and Denver formations are entitled to recognition as distinct formations. 



Am. Naturalist, \ ol. Will. 1889. p. 906. 



