584 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



tion may be studied in the region of Zapotitlan and San Juan Kyan. In 

 the Mesocretaceous, Aguilera includes the Mexican equivalents of the 

 Albian and Cenomanian. The Washita is sometimes correlated with the 

 Cenomanian, which is at the base of the European Upper Cretaceous, and 

 Stanton informs the writer that he regards the Upper Washita as probably 

 of Cenomanian time. 



The Comanchic faunas are mainly from calcareous sediments, and are 

 distinctly Mediterranean or southern European (especially Portugal and 

 Spain) in t} T pe. The echinoids present "a very familiar fades to a Euro- 

 pean eehinologist. . . . Several species are common European forms." 

 Out of six forms from Mexico described by Cotteau, "three are character- 

 istic of the European Lower Cretaceous (Aptian and Urgonian), namely, 

 Diplopodia malbosi, Salenia prestensis, and Pseudocidaris saussurei." 259 ' 

 There is nothing in common with the decidedly different faunas of the 

 Pacific border region of America. Each province develops distinct faunas 

 out of the previous Jurassic assemblage. 240 Eor this reason C. A. White 

 and Stanton 241 assume a complete land barrier along the Pacific, from 

 California to South America, during the Comanchic. 



The oldest Comanchic fauna, and one that the Mexican geologists 

 regard as older than the Trinity, occurs at Tehuacan, Mexico. It is a 

 fauna of reef corals and thick-shelled mollusks. Some of the common 

 corals are : Cryptoccenia cf . neocomiensis, Pttylloccenia cyclops, and Eugyra 

 cotteaui. There are also present the echinoid Pseudocidaris saussurei and 

 the mollusks Fimbria corrugata ?, Ostrea acuticosta, Trigonia plicatocos- 

 iata, CryptogerviUeia, Glaucoma bustamentii, G. cingulata, Nerinea cf. 

 loculata, and Tracliynerita nysti. 



Stanton 242 states that the Trinity has the foraminifer Orbitolina and 

 the following characteristic Mollusca: Trigonia stolleyi, T. crenulata, T. 

 lerclii, Requienia cf. texana, Mono pleura cf. marcida, M. cf. pinguiscula, 

 Natica pedernalis, Glauconia, branneri, G. cf. helvetica, and G. cf. picteti. 



The Fredericksburg, the time of greatest inundation, is marked by the 

 first abundance of Gryplima (several species formerly referred to G. 

 pitcheri) and Exogyra. In the Lower Fredericksburg there are forms of 

 Enallaster, Hemiaster, Epiaster, Holectypus, Schlcenbachia acutocarinata, 

 and 8. trinitensis. In the upper part of the Fredericksburg the fauna of 

 the southern region (Texas-Mexico) is in the main composed of Requi- 



239 Gregory : Bull, of the Geological Society of America, vol. 3, 1892. 

 2*° Stanton : Journal of Geology, vol. 5, 1897, pp. 579-624. 

 2« Stanton : Ibid., 1909, p. 417. 

 2*a Ibid., 1897. 



