48 



ANNALS NEW YORK ACADEMY OF SCIENCES 



heavy sandstones of the Lakota-Dakota series at the summit of the hog- 

 back. The first discoveries of remains of the large dinosaurs of the so- 

 called "Atlantosaurus fauna" were found about half way up the slope of 

 the hog-back, on the northern side of the gap, through which Bear Creek 

 crosses the hog-back. 



The hog-back is capped by a ledge of heavy cross-bedded sandstone of 

 the Dakota formation, underlain by white sands of the Lakota series. 



Beneath these sands are the soft sbales and clavs of the Morrison for- 



FiG. 6. — Tlie Mon'inuii foniiatiaa at Murritson, Colorado, looking east. 



mation. They are mostly pale green at this locality, with a few thin 

 bands of sandstone and some variegated clays and red sandstones. The 

 thickness here is evidently less than at Garden Park, near Caiion City, 

 farther south, but more than in the exposures farther north in Wyoming. 

 The upper and especially the lower contact could not be accurately deter- 

 mined. The formation appears to rest upon a coarse white sandstone, 

 which in turn rests on deep red sandstones of the Red Bed series. 



CANON" CITY AREA 



The Morrison formation is extremely well exposed in a number of 

 localities north of Caiion City. A structural basin of A-shape, formed 



