220 The Mesozoic Series of New Mexico. — Marcou. 
and to my great delight I saw that the Dakota group was 
identical with my Nova-Mexican Galisteo division of the 
upper Cretaceous; several fossils being identical, such as 
Ammonites per carinatus., Inoceramus prohlematicus, Ostrea 
congesta and fragments of fossil fishes. But more, I saw at 
once that the so-called lower Cretaceous of Messrs. Hall and 
Meek, was not lower Cretaceous at all, but far above the true 
lower Cretaceous or Neocomian of Texas and the Indian terri- 
tory, and even above the middle Cretaceous of Shawnee vil- 
lage (Indian territory) ; and I classified the Dakota group at 
its right place in the scale of American stratigraphy, as the 
inferior part of the upper Cretaceous or true Chalk division of 
Europe. At the same time I opposed the identification by 
Meek, Hayden and Hall of my Jurassic rocks of the Tucumcari 
area, with their Dakota group, insisting upon the absolute 
difference between the two systems ("Une reconnoissance 
ge'ologique au Nebraska," Paris, 1864 ; "Les phyllites cre'tacees 
du Nebraska, par J. Capellini et 0. Heer, Zurich, 1866; and 
*'Le terrain cretace des environs de Sioux City, de la mission 
des Omahas et de Tekama, sur les bords du Missouri," Paris, 
1886). 
The identification and synchronism of the Galisteo division of 
my survey of 1853, with the Dakota group of Sioux City, mod- 
ified my classification of the upper Cretaceous of New Mexico, 
reversing two subdivisions; for it was evident that the gray 
marls with Ptychodus, whipplei., Ammonites percarinaius, 
Inoceramus prohlejuaticus and Ostrea congesta of the 
northern vicinity of Galisteo, were at the base instead of the 
top of the New Mexican White Chalk. I was glad of it, for in 
my rapid reconnoissance of 1853, I had regarded and noted 
the Cretaceous sandstone opposite Albuquerque as the young- 
est member of the Cretaceous system in New Mexico ; but not 
having the time and occasion to follow the strata in order to 
see the contact of the three divisions established by me in the 
upper Cretaceous, I yielded with some reluctance to the 
palffiontologic rule, insisted upon by my friend Louis Agassiz, 
that the genus of fish Ptijchodus was characteristic of the 
utmost upper part of the White Chalk of England and France ; 
and as a consequence I made a slight mistake in the strati- 
graphy of the upper Cretaceous of New Mexico. 
