438 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 





autogrammes of vertebrates living on the land. Of dinosaurs, there are 

 certainly 17 species of Theropoda, with 18 of Predentata, to which may be 

 added 27 other species that are probable representatives of this order. Of 

 the bipedal carnivorous dinosaurs, three skeletons have been found (Anchi- 

 saurus colurus, A. solus, and Ammosaurus major) ; also, in addition to 

 Belodon, two other crocodilian skeletons of quadrupedal land reptiles 

 (Stegomus longipes and 8. arcuatus). In the black shales between the 

 extensive trap sheets occur many ferns, equisitales, cycads, and conifers, 

 besides ganoid fishes and the larva of a neuropterous insect — an assem- 

 blage that can be interpreted only as that of inland fresh waters. None 

 but animals and plants that inhabit the land are here seen, and when these 

 are considered in connection with the exceedingly common sun-cracked 

 layers of mud, less frequent raindrop impressions, local accumulations of 

 semi-rounded boulders, and the nearly constant lens-shaped bedding of 

 ihe imperfectly assorted sands and conglomerates between the muddier 

 layers of wider areal extent, the evidence is positive that the Newark 

 series is fluviatile in nature and must be eliminated from marine deposits 

 and Triassic seas. 



The writer has purposely dwelt at length on the Newark formations, 

 because similar beds are found at many horizons, and until recently these 

 have been regarded as of sea deposition. They must be eliminated from 

 marine deposits, however, and referred to the land, and will thus at times 

 very decidedly affect paleogeography. When continental deposits alter- 

 nate with marine horizons, as is especially the case during Pennsylvanic 

 time, such formations will naturally be mapped as marine. For a full 

 discussion of the areas of deposition and the internal structure of conti- 

 nental deposits, see Barrell. 33 



Continental seas are shallow. — It is very probable that a majority of the 

 periodic inundations of the North American continent resulted in very 

 shallow seas, perhaps rarely exceeding from 200 to 300 feet in depth. In 

 the discussion on later pages of this article, it is held that the continent is 

 a horst, that the great medial region remained practically unmoved, while 

 the margins were often folded and elevated. The sea periodically flowed 

 over this medial land — in fact, was elevated over it, owing to the detrital 

 materials unloaded into the oceanic areas, thus filling them and causing 

 them to spill over on to the lands. 



Along the western shorelines of Appalachia, conglomerates, sandstones, 

 and coarse muds bearing ripple-marks are constantly met with, while dur- 



33 Barrell: Journal of Geology, Chicago, vol. 14, 1906, pp. 316-356, 430-457, 524-568. 

 Ibidem, vol. 16, 1908, pp. 159-190, 255-296, 363-384. Bull. Geological Society of Amer- 

 ica, vol. 18, 1907, pp. 449-476. 



