26 



Weber River beds to Dr. Hayden. 1 - To near the same horizon are perhaps to 

 be referred the coal observed by Professor Marsh 2 on the south side of the 

 Uintah Mountains in Utah, which were overlaid by strata containing Ostrea 

 congesta. This may, indeed, be referred to a still older period, as that oyster 

 is characteristic of No. 3, according to Meek and Hayden. The Placer 

 Mountain and Cafion City groups are nearer to No. 5, but the precise relation 

 to it has not yet been determined. I therefore proceed to the proper and 

 original Fort Union epoch as defined by Hayden. 



This extended deposit is stated by Hayden 3 to extend from the Missouri 

 Valley to Colorado, passing under Tertiary beds by the way. That this is 

 the case has been confirmed by the researches conducted in the northern and 

 eastern portions of Colorado during the season of 1873 by the writer - . 4 I 

 present comparative lists of the vertebrate species known from the Platte 

 and Missouri Valleys in the respective Territories. 



COLORADO. 



Compsemys victus. 

 Adocus lineolatus. 

 Plastomenus punctulatus. 

 Plasotmenus insignis. 

 Trionyx vagans. 



Boltusaurus jwrugosus. 

 Polyonax mortuarius. 

 Cionodon arctatus. 

 I'Luhosaurus ? Occident alls. 



DAKOTA. 



Compsemys victus. 

 Adocus lineolatus. 



Plastomen us punctulatus. 



* * * * 



Trionyx vagans. 

 Ischyrosaurus an tiquus. 

 Plesiosaurus occiduus. 

 *- * * * 



* * * * 



* * -X * 



Hadrosaurus occidentalis. 



The identity and correspondence of the species in the two columns indi- 

 cate that these remote localities contain the remains of the same fauna. 

 Further, the presence of Dinosauria and Sauropterygia demonstrates its 

 mesozoic character. 



A number of vertebrate remains was collected by George W. Dawson, 



'Annual Report, 1870, p. 168. 



! Sco an interesting article by Prof. O. C. Marsh on the Geology of th<? Eastern Uintah Mountains 

 in the American Journal of Science and Arts for March, 1871. 

 'Annual Report Colorado, 1869, p. 89. 

 *.-ir I'm Mr i in i>i 'iii.- I ni ted States Geological Survey, No. 1, 1874, p. 10. 



