CORBELATIOX OF WYOMING F« >RM ATI OX. T.T 



of the Front or Colorado Range there was a much greater development of 

 Red Beds than on the eastern, and that their lower portion, which is more 

 of a chocolate or maroon-red color, graded insensibly into a series of strata 

 containing Carboniferous fossils. These facts tend to show thai a pari 

 of what had been originally mapped ;is Trias may more properly be 

 considered Upper Carboniferous or Permo-Carboniferous; but enough 

 paleontological evidence has accumulated to justify the assumption that 

 the upper part of the seiies, the Red Beds proper, tin- Wyoming formation, 

 is probably Triassic. 



This latter evidence rests, first, on the discovery by Dr. A. C. Peale in 

 southeastern Idaho of Triassic and Jurassic fossils, which were later deter- 

 mined and discussed l>v Dr. C. A. White. 1 



Among these forms, those regarded l>v Dr. White as of distinctly 

 Triassic character are Meekoceras aplanatum, Meekoceras mushbachamim, 



Meekoceras gracilitatis, Arcestesf cirratus, Arcestes f, Arcestes /, 



Eumicrotis curta, Avicvdopectenf pealei, A.! alius, A..' idahoensis, Terebratula 

 semisimplex, T. augusta. The Jurassic forms embraced Pentacrinus asteriscus, 

 Belemnites densus, Camptonectes bellistriatus (of .Meek ami Hayden), ami 

 Eumicrotis curta, and were obtained from the same locality, but from 

 different ami much higher strata. Between these two distinct horizons 

 are found the "lied Beds," which Dr. Peale regards as the equivalents of 

 the led Beds east of the Rocky .Mountains, from identity of lithological 

 characters and manner of occurrence. 



Dr. White, in his remark- on the above fossils*, Mate- that "some of the 

 types in which these tonus are expressed are, as originally pointed out by 

 Professor Hyatt, such as in Europe are regarded as characteristic of the 

 Middle Trias — the Muschelkalk." This reference indicates thai at leasl a 

 portion of the lied Beds, in certain localities, may properly he regarded as 



Triassic, and though Drs. White and Peale employ the evidence of the 

 fossils especially by way of distinguishing the Jura and Trias as separate 

 formations in the Rocky .Mountains the results may !«• equally well 



'Jura-Trias section of southeastern Idaho. Bull. U. S. Geol. and Geog. Surv. Terr. (Hayden), 

 Vol. V, 1871, ]>. llii; Fossils of the Jura-Trias of southern Idaho, ibid., p. 115; rriassic fossils of 

 southeastern Idaho, U. S. Geol, and Geog. Surv. Ti-i t. (Hayden . Vol. XII, 1878, p. L05; Invertebrate 

 Paleontology, No. V, Triassic fossils of southeastern Idaho, by C. A. White. 



