1890.] NATURAL SCIENCES OF PHILADELPHIA. 459 



Dr. White mentions' the occurrence of heavy depoi^its of hard 

 blue limestone of the Comanche series in the Sierra San Carlos, in 

 the State of Chihuahua, 75 miles southeastward of Presidio del 

 Norte ; the beds are here said to have a thickness of not less than 

 4000 feet, and are thrown into a nearly vertical position, with the 

 so-called "Upper" Cretaceous beds lying conformably on their east- 

 ern face. It is probably from the lower portion of this series that 

 Wislizenus obtained (tlirough presentation) the Peden qninque-cos- 

 tatus (Cenomanian), Avhich was reported to have come from a local- 

 ity, near Corralitas, "about 250 miles northwest of Chihuahua."' 



The numerous localities that have here been cited for the occur- 

 rence of Cretaceous fossils on and beyond the Mexican plateau in- 

 dicate the broad range over which the deposits of the period -were 

 laid down ; there can be little or no question that all the outcrops 

 that have been observed are either now united continuously with one 

 another, or had been so united during the time of their formation 

 and uplift. The great volcanic outpourings which followed the 

 catastrophic uplift have largely obscured the giant masses of the 

 formations, whose full forms are still so beautifully displayed along 

 the eastern and southern edges of the plateau, but we find the con- 

 nections in the scattered islands or oases of rock which have from 

 time to time been noted in the interior states. 



The preceding references cover outcrops in the States of Sonora, 

 Chihuahua, Coahuila, Nuevo Leon (?), San Luis Potosi, Hidalgo, 

 Vera Cruz, Puebla, Mexico, Morelos and Guerero, but the forma- 

 tion has also been identified in Jalisco, Colima,^ Zacatecas (at Noria 

 de Angeles, Fresnillo, Veta Grande, etc., along the spurs or exten- 

 sions of the Asientos Mountains of Aguascalientes), Aguascalientes 

 (district of the Cerro de Temascal, the Asientos Mountains),* Que- 

 retaro (district of the " Doctor"), and Michoacan (district of Coal- 

 coman).^ Over all this area there is a remarkable similarity in the 



1 Am. Joiiin. Science, 1889, part 2, p. 444. 



^ Op. cit., p. 138. 



3 On the authority of Antonio del Castillo, as stated by Barcena — Datos para 

 el Estudio de las Rocas Mesozoicas de Mexico, p. 34. 



* Barcena, Noticia Geologica del Estado de Aguascalientes, 1876, p. 2. 



^ Urquiza, Exploracion del Distrito de Coalcoman, Estado de Michoacan — 

 Anales del Ministerio de Fomento, VII, 1882. The fossils found in this region 

 have been referred by Urquiza to Hipptirites hioculata, H. calami (if ortnis, H. Mex- 

 icana, Radiolites turbinattis, R. foliacetis ? Astarte sp. indet., Pecten sp. indet.. 



