•546 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



Neodevonic faunas of eastern America are varied, and are not nearly so 

 uniform in composition as those of the Hamilton. 



In the Cordilleran sea within the area of the United States, from Ari- 

 zona (Martin and Lower Globe formations) and California (Kennett 

 formation) east to Iowa, occurs the Lime creek or Spirifer hungerfordi 

 fauna, clearly of Euro- Asiatic derivation. In the Manitoba region, Tyr- 

 rell has collected and Whiteaves has described a late Mesodevonic fauna 

 characterized by the well known European Stringocephalus burtini. It 

 is their Winnipegosan biota, together with Neodevonic forms, as Gy- 

 pidula comis, Pugnus pugnus, and Stropheodonta interstrialis. This dolo- 

 mite, 100 feet in depth, is followed by the Manitoban limestone and shale 

 (with brine springs), 200 feet in thickness, apparently equivalent to the 

 Lime creek of Iowa. The Manitoban fauna is widespread in Alberta, 

 Athabasca, Mackenzie, and Yukon regions, extending to the Arctic ocean. 

 It was first described by Meek, and has since been revised by Whiteaves. 

 In these northern areas some salt and more gypsum are present. 



Another late Devonic fauna with a peculiar and distinct aspect is that 

 of the Lower Ouray of Colorado, described by Girty, and very recently by 

 Kindle. 



The youngest of the western Devonic horizons appears to be the Three 

 Forks shale of Montana, described by Peale. The lower 70 feet of shale and 

 argillaceous limestone have no fossils, but are followed by about 30 feet of 

 green, black, and argillaceous shales crowded with Upper Devonic fossils, 

 of which Spirifer whitneyi is the most common. Eecently Eaymond 164 

 has described the faunule from the lower beds of the upper Three 

 Forks shale, of which the following are the more characteristic forms: 

 Camarotcechia contracta, Leiorliynchus mesacostale, Spirifer pinonensis, 

 Cleiothyridina devonica, Locopteria holzapfeli, Platyclymenia americana, 

 P. polypleura, Prolobites simplex, Tornoceras crebsiseptum, and T. doug- 

 lassi. At the top of the Three Forks, and beneath the Madison, occurs a 

 "yellow laminated sandstone 25 feet thick" (Peale), having a very differ- 

 ent fauna. This was shown the writer by Eaymond. Among the fossils 

 Syringotliyris carteri and Spirifer cf. striatus are prominent. This fau- 

 nule is to be compared with that of the lower Louisiana limestone of Pike 

 county, Missouri. Therefore there is here, as in the Mississippi valley, a 

 break in deposition clearly distinguishing the Devonic, both physically 

 and faunally, from the Mississippic. 



The Alaskan Devonic has been described bv Kindle. 165 



164 Raymond: American Journal of Science, vol. 23, 1907. Annals of the Carnegie 

 Museum, vol. 5, 1909. 



165 Kindle : Bull. Geological Society of America, vol. 19, 1908. Journal of Geology, 

 vol. 15, 1907. 



