NATURAL SCIENCES OP PHILADELPHIA. 267 



Red and gray marls ( Wahsatch ) . . . . 1500 



Sandstone ( Group J 1000 



Green and black marls Puerco group .... 500 



3000 



The following is an approximate estimate of the mesozoic beds 

 in the same region; as they were not accurately measured,. the 

 numbers will have to undergo revision ; their relative thickness is 

 nearly as given : 



Uncertain (concealed in the sage plain) . . . . 500 



Cretaceous No. 4 1500 



Cretaceous No. 3 400 



Cretaceous No. 2 1500 



Cretaceous No. 1 500 



Jurassic 600 



" Trias" (bottom not seen) 1000 



Total 6000 



The mesozoic beds of this section (excepting some of the higher 

 members of the cretaceous) have been examined over extensive 

 areas to the west and south, by Messrs. Marcou and Newberry, 

 whose valuable reports accompany those of Lieutenants Whipple 

 and Ives, on the routes surveyed by them through Arizona and 

 New Mexico. The horizon here termed, after Hayden, "Triassic," 

 has been referred to this formation by Marcou also, who had the 

 opportunity of examining it in Texas and the Indian Territory. 

 So far as the latter region is concerned, I can confirm the identifica- 

 tion, having examined bones from the red beds of that country, 

 which appear to be those of Belodonts. Dr. Newberry terms it, 

 in Arizona, the " salt group," or " saliferous sandstones," referring 

 to it as probably including both Triassic and Permian strata. 



The formations here called Jurassic are partially included by 

 Marcou in his triassic series ; and are termed the " variegated 

 marls" by Dr. Newberry, who is inclined to refer them to the 

 Jurassic. 



Dr. LeConte inquired, at what line of latitude the observations 

 of Mr. Cope had been made. Mr. Cope replied that the section 

 was made at about the 36th degree. 



Dr. LeConte then remarked that the observations of Mr. Cope, 

 with a single exception of the locality of fossils mentioned, which 

 was new, confirmed entirely the observations made by himself in 

 1867 ; the arrangement of the older beds further south was, how- 

 ever, less simple than that indicated on the blackboard by Mr. 

 Cope. Underneath the red triassic beds mentioned by Mr. Cope 

 was a very thick bed of hard, white sandstone of Permian age, 

 which bore a deceptive resemblance to Cretaceous No. 1, but which 

 along the Pecos River contained an abundance of Calamites, and 

 other characteristic plants. Below this white sandstone was a 



