330 Annals of the Carnegie Museum. 



Marsh has called these beds the Atlantosaiinis beds, while Cross 

 several years later named the same series the Morrison formation, re- 

 ferring it to the Juratrias. There would seem to be little doubt that 

 the entire series may be very properly referred to the Jurassic on the 

 evidence of the dinosaurian remains which they contain, all of which 

 so far as at present known pertain to Jurassic types rather than Tri- 

 assic. The beds of sandstone, marl and shale are not continuous, so 

 that a section taken at any given point showing the arrangement of 

 the different components would vary greatly from another taken at a 

 different though not far distant place. The ripple-marks, cross-bed- 

 ding and discontinuity of the component strata, as well as the pres- 

 ence of fossil footprints and the character of the invertebrate and plant 

 remains found in the beds, all bear evidence of the prevailing condi- 

 tions attending the deposition of the materials. These conditions 

 will be discussed later when we come to speak of the bone deposits 

 which they contain. 



The sandstones, shales and marls of the Jura may be seen in the en- 

 closing walls on either side of the southern half of Garden Park, and 

 in the canon of the creek below the park, which affords several splendid 

 sections between the mouth of the cailon and the southern entrance 

 to the Park. In general the beds have a gentle southerly dip, but 

 within the cailon this dip and the general sequence of the strata is fre- 

 quently obscured by numerous local faults and landslides. z\t the 

 mouth of the caiion about four miles distant from Canyon City the 

 strata are inclined at a high angle and soon pass beneath the surface. 



Cretaceous. 

 T/ic Dakota Sandstones. — Conformably overlying the Jurassic de- 

 posits is a series of yellowish-brown or whitish sandstones with occa- 

 sional layers of shale. These sandstones and shales so closely resemble 

 the underlying Jurassic deposits both as regards their physical appear- 

 ance and constituent parts that it is impossible to definitely separate 

 the two series, and any line of demarcation between the two deposits 

 must be considered as somewhat arbitrary. Cross has placed the 

 thickness of the Jurassic or Morrison formation at 350 feet, while to 

 the Dakota he assigns a thickness of 300 feet. This appears to the 

 writer as placing the base of the Dakota somewhat too low in the 

 series, and I think by allowing so great a thickness as 300 feet for the 

 Dakota they would be made to include the upper and perhaps a second 



