552 



INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



tions are regarded as representatives of the Russian Volgien (Jurassic) and in a 

 general way the Alamitos corresponds with the lower Volgien or Tithon, but the 

 Kimmeridge may be represented in it. The Cienegiiita, which is distinguished 

 by an abundance of Aucella, represents the upper Volgien or Neocomien (Lower 

 Cretaceous). 



F 17-18. CUBA. 



T. W. Vaughan contributes the following notes on the Jurassic of Cuba: 



Strata of Jurassic age have been reported from Cuba and the Isle of Pines since the time 

 of Humboldt. Recently Dr. Carlos de la Torre has collected Jurassic ammonites, referred by 

 him to the genus Idoceras, in the vicinity of Vinales, and has published excellent photographic 

 illustrations.'^ Dr. T. W. Stanton agrees with De la Torre in considering these ammonites of 

 Jurassic age. Jxurassic hmestone forms the axial portion of the Sierra Organos, in the Province 

 of Pinar del Rio, and is the oldest geologic formation revealed in a cross section of the island 

 taken along a line passing through Vinales, in the vicinity of which are excellent exposures. 

 The limestone is hard and blue, and, though not distinctly crystalline, it is intersected by 

 small white veins of calcite. 



Overlying the Jurassic limestone, south of Vinales along the road to Pinar del Rio, are 

 reddish argillaceous schists, which form two parallel ridges. These schists were evidently 

 derived from the metamorphism of a shale series that contained a few bfeds of sandstone and' 

 some layers of limestone. 



G 13-14. SIERRA DE MAZAPIL, ZACATECAS AND COAHUILA. 



Burckhardt ™ has classified and described the Jurassic and Cretaceous of the 

 Sierra de Mazapil district, in the "Mesa Central" of Mexico, as follows: 



Jurassic and Cretaceous series of the Sierra de Mazapil and Santa Rosa. 



o An. Acad. cien. Habana, Rev. cien., vol. 47, July, 1910, pi. facing p. 22. 



