126 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



while they were conformable with the San Juan they had 

 been folded and eroded prior to the deposition of the suc- 

 ceeding sands and limestones of the basal Eocene. This is 

 shown on the Salinas River at Ramones where there is a bed 

 of sandstone lying in discordant stratification directly upon 

 the crumpled and folded Papagallos shales. In this sand- 

 stone were found : 



Venericardia alticostata 

 V. planicosta 

 Ostrea pulaskensis 

 Cucullaea macrodonta 



These fossils are characteristic of the Midway, the lowest 

 stage of the Gulf Tertiaries. There can, therefore, be no 

 question as to the Cretaceous age of the Papagallos shales at 

 the type locality. 



Similar limestones and shales were found at San Felipe and 

 Valles, west of Tampico, but here they were without fossils. 

 Jeffreys called the former the San Felipe beds and applied 

 the term Mendez to the overlying shale and its upward con- 

 tinuation east of the Sierra del Abra. With the idea that 

 these were the continuations of the San Juan and Papagal- 

 los, Cummins traced the beds from the Papagallos Hills to 

 Mendez and Valles. 



It is about 10 miles from the Papagallos Hills where both 

 San Juan and Papagallos formations occur, to San Juan on 

 the railroad between Tampico and Monterey. Over that dis- 

 tance the shales are exposed in all the ravines and are the 

 surface rocks except where covered by superficial drift. On 

 the south side of the San Juan River, south of the town of San 

 Juan, there is a fine exposure of the beds in a railroad cut. 

 From San Juan to Montemorelos is 26 miles. The shales 

 are seen at numerous places between these points, and only 

 at such places as are drift-covered was the shale not seen. 

 East of Montemorelos there are hills that are composed en- 

 tirely of the shales. A trip of 9 miles was made west of the 

 town toward the Sierra Madres, and after getting out of the 

 river valley the road was continuously on the shales. Be- 

 tween Montemorelos and Linares, a distance of 32 miles, out- 

 crops of the shales are numerous and they are also shown in 



