C. A. White—Jura-Trias of North America. 217 
strata in question to be about 3,000 feet in thickness of alter- 
nating limestones, sandy shales and sandstones, with about 
1,800 feet of Carboniferous strata beneath them, and with 
which they are apparently strictly conformable. He found in 
that immediate vicinity no exposures of the Red Beds, which 
have so generally been referred to the Trias, but he recog- 
nized them at some localities only a few miles away ; and he is 
confident that they occupy a position immediately above the 
uppermost strata of the series exposed at the locality here 
especially referred to. It thus appears that this fossiliferous 
series, containing true Triassic types, occupies a position beneat 
the comparatively unfossiliferous Red Beds which were so long 
supposed to be the only representatives of the Trias in that great 
region ; and that they separate the former from the well-known 
Jurassic series. The fossils of this lower series were found at 
different horizons within the thickness of 3,000 feet exposed at 
the locality mentioned, the following being a list of them: 
1. Terebratula semisimplex White ; 2. T. augusta Hall & Whit- 
field? ; 8. Aviculopecten Idahoensis Meek; 4. A. Pealei W.; 5. A. 
altus W.: 6. Humicrotis curta Hall; 7. Meekoceras aplanatum W. ; 
8. M. Mushbachanus W.; 9. M. gracilitatus W.; 10. Arcestes ? 
etrratus W.; 11. A. ? ? 
them to him for examination, and of the two, or perhaps three, 
generic forms which they embrace he describes one as new, 
