V 175-200 feet. 



COMO ANTICLINAL. 91 



by Dakota sandstone, which serves as the capping-stone to the ridg-e, and 

 the overlying rock on the southern and gentler slope. Nov^here in the Rocky 

 Mountain region, within the belt of exploration, are Jurassic rocks better 

 defined, exhibiting all the characteristic strata which have been observed 

 in other localities, and at the same time associated with organic remains 

 about the age of which there can be no doubt. 



The following section along the bluff-face of the ridge was taken from 



top to base, in descending series : 



DaJcota Cretaceous. 



1. Compact yellowish-browu sandstone, forming the summit of the ridge. 



Jurassic, 



2. Gray sandy marl 



3. Cream-colored marls, with sandstone layers 



4. Bluish-drab cherty limestone 



5. Fine ash-colored marls, with thin beds of light-colored limestone., 



6. Gray and Orange marls, with coarse sandy material 



7. Eeddish-yellow sandstone j 



Triassic ? 



8. Brick red compact sandstone. 



The Dakota beds are a dense, tough series of sandstones, distinctly 

 bedded, and breaking up into rough angular blocks in a similar manner as 

 observed east of the Colorado Eange. In the Jurassic, the bluish-drab 

 limestone, which is everywhere so persistent a stratum, is here well devel- 

 oped, of a characteristic light drab color, flinty fracture, and carrying 

 numerous small calcite crystals, scattered through the rock. Diligent 

 search was made in this limestone for fossiliferous remains, but without 

 success. In the marls and limestones, however, both above and below it, 

 occur well-marked forms, which are sufficient to prove the Jurassic age of 

 this horizon, although no very great variety in species has been identified. 



The following species have been found by our parties : 



CRINOIDS. 



Segments of the column of Pentacrinus asteriscus 



CEPHALOPODA. 



Belemnites densus. 



LAMELLIBRANCHIATA. 



Tancredia Warreniana. 

 Trigonia quadrangular is, h. sp. 



