590 C. SCHTJCHERT PALEOGEOGRAPHY OF XORTH AMERICA 



Division, associated with Eocene fossils (ibid., 129). It is probable that 

 the Bine Mountain series is also present on Haiti, Costa Eica, and Cuba. 



Apparently the same fanna occurs in northern Guatemala. Sapper 251 

 mentions Barrettia and Sphcerulites. The formation consists of lime- 

 stones, dolomite, limestone breccias, and gypsum, with some salt. 



The Comanchic echinoids of the Antillean-Mexican region, as has been 

 seen, are very closely related to those of southern Europe, but in the Cre- 

 tacic "the two faunas developed on independent lines/' This differentia- 

 tion of the echinoids of the two areas continued into the Cenozoic. 252 



Colorado series. — The vast area east of the Eocky mountains, from 

 Colorado to the Arctic ocean, which remained elevated throughout the 

 Mesozoic, began to be invaded by the ocean during the early Cretacic. 

 The southern Comanchic submergence had mainly vanished, and early in 

 Dakota time the Gulf again spread toward the north. The submergence 

 thus begun was continued northward rapidly during the Benton, and it is 

 quite likely that at about the same time the Arctic extended southward 

 and united with these southern waters. This, then, was the great inland 

 Coloradoan sea, with its deposits resting unconformably upon various of 

 the earlier formations. 



The Dakota fauna, as published, is a small one of brackish-water forms 

 and Unios, with a few marine species. Stanton 253 states that "the fresh- 

 water species show relationship through the genus Pyrgulifera with the 

 fauna of the Bear Eiver formation, which is apparently about on the 

 horizon of or a little later than the Dakota. The Bear Eiver fauna of" 

 C. A. White 254 "is unique among western non-marine faunas in that it 

 contains a number of types that have left no descendants in later forma- 

 tions of the region." The flora of the Dakota has over 500 species, the 

 angiosperms being dominant throughout all the horizons. 



Succeeding the Dakota is the Colorado series, which is divided into a 

 lower portion, the Benton, and an upper, the Mobrara, but not every- 

 where can this two-fold separation be maintained. The Colorado series 

 is characterized by Inoceramus labiatus, and extends from the Gulf of 

 Mexico probably to the Arctic ocean, yet in the Gulf area east of western 

 Arkansas and along the Atlantic coast no deposits of this time are known.. 

 The diagnostic fossils of the Colorado are: Inoceramus labiatus, I. dimi- 

 dius, I. fragilis, I. deformis, I. undabundus, Ostrea lugubris, Exogyra 



251 Sapper : Petermann's Mittheilungen, Erganzungsheft, 1894, p. 113. 



252 Gregory : Bull, of the Geological Society of America, vol. 3, 1902. 



253 Stanton : Journal of Geology, 1909. 



254 White : Bull. no. 128, TJ. S. Geological Survey. See also Stanton, American Journal 

 of Science, vol. 43, 1892; Veatch, Professional Paper no. 56, U. S. Geological Survey,. 

 1908. 



