290 The American Geologist. November, leos 
a close analogy in the New Mexican sequence. The full 
force of this position finds another instructive parallel in 
the so-callecl Permian question of central Kansas. t 
Both of these controversies doubtlessly would have 
been avoided had all participants relied less on analogy and 
more upon the actual critical criteria which the formations 
themselves supply. 
Singularly enough, after all these years in which Mar- 
co. 1 has stoutly maintained the correctness of his original 
position, the "Triassic" part of the Tucumcari section ap- 
pears finally to be determined without much doubt as Tri- 
assic in age. It now. becomes a question of more than 
passing interest to inquire anew regarding Marcou's Jurassic 
beds of the same locality. 
According to Marcou's Pyramid mountain section, 
which is near the Cerro Tucumcari, and which is essentially 
the same, there were included in his so-called Jurassic 
sequence (a) about 225 feet of soft, shaly, light-colored 
sandstones, which Hill has since correlated with the Trinity 
sands of central Texas, (b) 50 feet of bluish fossiliferous 
shales, which Hill considers as forming the uppermost por- 
iton of the Washita division of the Comanche series, and 
from which Marcou collected his few fossils, and (c) 50 feet 
of massive yellow calcareous sandstone, which has since 
been found to be the attenuated extension of the Dakota 
sandstone. Even within the last decade Cummins has 
gathered all of these beds into a single unit and proposed 
for them the title of the Tucumcari formation.* All of 
these formations at Tucumcari appear to form a perfectly 
conformable succession. 
More extended observations have lately shown quite 
conclusively that marked unconformities actually exist be- 
tween everyone of the formations mentioned. Regarding 
them many questions now arise concerning their real sig- 
nificance in the geological history of the region. 
The remnant of the Dakota sandstone (c) which is 
found in the Tucumcari section is now known to form the 
base of the Mid-Cretaceous (Upper Cretaceous of Meek 
* Journal of Gpologv. vol. vii, pp. 221-241. 1899. 
* Texas Geol. Sur., Third Ann. Rept., p. 201, 1892. 
