J70 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4tii Ser. 



than that zone, although its fauna is composed of strictly 

 Mesozoic types, of which the genus Sphenodiscus is the most 

 striking example." 



Papagallos Shale 



To the west of the final exposure of the Escondido beds 

 near the Pescado Ranch and apparently dipping under them, 

 there is a series of very fine-grained blue or black limy clay 

 shales, weathering brown, yellow or white, in which we have 

 so far found no fossils. These shales carry both selenite and 

 barite and weather into slaty particles. These shales were 

 first studied by us in the Papagallos Hills west of Ramones 

 and we have given them this name. The Papagallos shales 

 are exposed along the western border of this area from the 

 San Antonio Range, on the north, nearly to Tordo Bay and 

 are also found over extensive areas south and west of the 

 Tamaulipas Range. They overlie the gray limestone of the 

 San Juan and have a very considerable thickness. 



San Juan Limestone 



Exposures in various canyons of the Tamaulipas Range 

 show, underlying the Papagallos shales, a series of thin to 

 medium bedded gray limestones with Inocerami and Am- 

 monites. The fossils so far found are not very well pre- 

 served, but the Ammonites seem to fix the age as equivalent 

 to the Taylor or Austin beds of the Texas Cretaceous. In 

 a few places the Tertiary beds iDverlap the Papagallos and 

 rest directly upon these limestones. 



South and west of the Tamaulipas Range the Papagallos 

 shales and San Juan limestones occupy a very large area, 

 overlie the Tamasopa limestone, which is the top of the 

 Middle Cretaceous, and represent the entire series of Upper 

 Cretaceous beds of the Mexican geologists as known here. 



The exact correlation of these beds with those of the 

 Texas section is not yet possible, as they represent an en- 

 tirely different phase of deposition and carry so few fossils. 



The upper Tamasopa limestone around Micos is corre- 

 lated by Bose^ with the Woodbine or Timber Creek beds 

 of the Upper Cretaceous of Texas, which is probably of the 

 same age as the Dakota of the interior region. 



3 Bose, E., "Neue Beitrage zur Kentniss der Mex. Kreide," p. 10, 1910. 



