COMANCHIC PERIOD 583 



to 30 feet. The total thickness of all the coal seen is 137 feet. The 

 plants indicate Upper Jurassic age, but not so young as Wealden. 



On Prince Patricks land (latitude 76° 20' north, longitude 117° 20' 

 west) were found the marine fossils Harpoceras macclintocfci and Monotis 

 septentrionalis. On North Cornwall (latitude 77° 30' north, longitude 

 95° west) Belcher found vertebrae of Ichthyosaurus. 



Comanchic Period 

 See plates 91 to 93 



The highly emergent condition of the North American continent con- 

 tinued into the Comanchic, and the only marine areas of this time were 

 the widely extended formations in the Gulf of Mexico region and the re- 

 stricted series along the Pacific. Continental deposits devoid of marine 

 fossils occur in a limited area along the Atlantic Piedmont, but sediments 

 of this nature with a far greater distribution are present in the northern 

 'Great Plains region and extend into Canada. 236 



Table of Texas Comanchic Formations 



Washita series : Comanche Peak. 



Buda. Walnut. 



Denison (Del Rio) . Trinity series : 



Fort Worth. Paluxy. 



Preston. Glen Rose. 



Fredericksburg series : Travis Peak. 

 Edwards. 



"—■'-■*• %J 



Gulf of Mexico area. — From Arkansas to southern Mexico occurs the 



greater development of the Comanchic or the "Lower Cretaceous." The 

 Comanche series was defined by Hill to embrace his Trinity, Fredericks- 

 burg, and Washita divisions. In central Texas the thickness of these 

 •deposits is about 1,500 feet, which increases to 4,000 feet of limestone to 

 the southwest of Chihuahua, and is said to attain far greater depth in cen- 

 tral Mexico. 237 



Aguilera 238 divides the entire Mexican "Cretaceous" into Eo, Meso, and 

 Neocretaceous, because the series, being devoid of recognizable breaks in 

 sedimentation, is seemingly a continuous one. The Eocretaceous of Mex- 

 ico is not yet characterized paleontologically, but is thought to represent 

 the Neocomian, Barremian, and Aptian of southern Europe. A good sec- 



236 For a digest of the literature up to 1890, see White : Bull. no. 82, U. S. Geological 

 Survey, 1891. 



237 Hill : Bull, of the Geological Society of America, vol. 5, 1893, pp. 297-338. 



238 Aguilera : Guide International Geological Congress, Mexico, 1906. 



