TO JUNCTION OF GRAND AND GREEN EIVERS. 91 



Section of the cliffs of Canon Pintado. 



Feet. 



1. Coarse yellow sandstone, floor of Sage-plain 200 



2. Gray and green shales, interstratified with coarse gray sandstones and yellow 



conglomerate 250 



3. Red and green shales, with bands of whitish and greenish sandstone, with silici- 



fied wood and Saurian bones - . 350 



4. Yellow and red massive calcareous sandstones 200 



In the foregoing section No. 1 is the Lower Cretaceous sandstone forming the 

 surface-rock over all the country lying Iretween the Sierra La Plata and Sierra Abajo. 

 A short distance back from the canon it is overlaid by patches of shale with Gryphaeas, 

 and therefore represents the surface of the Lower Cretaceous group. No. 2 is proba- 

 bly also Cretaceous, though here containing no fossils by which this question could be 

 determined with certainty. A group of rocks, having similar lithological characters, 

 at the Moqui villages, lies between the red beds below and the massive leaf-bearing 

 sandstones above, and there contains Ammonites percannatus and other Lower Creta- 

 ceous fossils. As will be seen in the progress of our geological narrative, at interme- 

 diate points on the San Juan a thickness of several hundred feet of soft green sand- 

 stones and green sandy shales separates the coarse yellow sandstones (the floor of the 

 Sage-plain) from the red gypsiferous rocks below. Until fossils shall be discovered in 

 these beds, it will be impossible to draw any sharply defined line marking the base of 

 the Cretaceous formation; and since the strata are here everywhere conformable, it is 

 extremely doubtful whether any such line of demarcation exists in nature. 



Saurian bones. On the north side of the canon just opposite our camp (26), in the 

 face of the cliff, about 250 feet above its base, I discovered the bones of a large Saurian. 

 Probably the greater part of the skeleton is still imbedded in the rock, as, although I spent 

 two days, with several assistants, in excavating at this point, the tools at our command 

 were too light for such heavy work as it proved to be, and we were compelled to 

 leave many bones, which we could see, but had not the means to extricate from their 

 envelopes. The special object of our efforts, the head, was not reached, but still 

 remains to reward some future geologist who shall visit this interesting locality, with 

 more time at his command and more adequate implements for rock excavation than 

 we possessed. The bones we obtained were mainly those of the extremities: a femur 

 entire; the greater part of a humerus; several of the phalanges of the[toes; portions of 

 the ribs, and other large and, to me, quite incomprehensible bones. All of these have 

 been placed in the hands of the distinguished anatomist, Professor Leidy, who will 

 make them the subject of a special report. The size of the animal, as indicated by 

 these bones, must have been very large. The femur taken out measured 30 inches in 

 length, by 4 in diameter, at its smallest part, the articulations being much thicker. A 

 portion of the scapula which was taken out was 22 inches long and 16 wide at the 

 broadest part, and this but a fragment. 



Near the locality where the larger skeleton was found a part of a rib of a smaller 

 individual was picked up, and on the opposite side of the valley a shapeless fragment 

 of a large bone was found at the foot of the cliff. From these facts it is evident that 



