MARCOU: THE JURA OF TEXAS. 
153 
paleontological grounds only, without any regard to stratigraphy, 
and we may add against a well-balanced and correct stratigraphical 
classification, for there is no reason whatever to suppose that the 
Jurassic deposits are missing above the Trias in the Tucumcari 
area. 
The points in question are the correct determination of fossil 
remains and whether the evidence of Cretaceous types warrants the 
setting aside and complete disregarding of the Jurassic types which 
are found to be numerous, even according to Messrs. Humble and 
Cummins. 
Let us consider the fossils from subdivisions 55 and 5c, sent me by 
Mr. Humble. First, the Gryphaea Pitcheri is not the G. Pitcheri 
figured by me in Geology of North America, pi. 4, figs. 5 and 6- 
Mr. Humble has sent me four specimens of Gryphaea, of which 
two belong to a small species having some affinities with Gryphaea 
arcuata of the European Lias, and the other two larger ones to 
another species. Both are species of Jurassic forms and have no 
relation to the Gryphaea Pitcheri 1 of my Geology of North 
America. 
Second, the Gryphaea dilatata var. Tacumcarii is well deter¬ 
mined by Mr. Humble; there is no doubt about its identity with the 
s}:>ecies so common in the Tucumcari area in New Mexico. 
Third, the Terebratula wacoensis Rom. is very closely related to, 
if not absolutely identical with, the Terebratula ovatissima Quen- 
stedt, of the Lower Lias of Wurtemberg, and consequently is a 
Jurassic form. Nothing: like it has ever been found in the Neoco- 
mian of the Jura Mountains. 
Fourth, the Ammonites leonensis Conrad is not that species but 
is the Ammonites iShumardi Marcou, figured in Geology of North 
America, pi. 1, fig. 1, la. It is true, that I placed this species in the 
Cretaceous of Texas, but I was impressed by its form, and say at 
p. 33, “ This species differs from all the Cretaceous Ammonites 
hitherto described ; it resembles slightly the A. coronatus of the 
Oxfordian.” If the specimen had come to me with a Gryphaea 
Tucumcarii , I should not have hesitated to refer it to the Jurassic 
of Texas. But it came into my hands among a lot of Cretaceous 
fossils collected by a person, not a geologist, who put together all 
the fossils obtained during a military march through Texas. 
1 As long ago as 1861 in order to prevent further confusion, I gave to the Gryphaea Pit¬ 
cheri of Romer and Marcou and the G. Pitcheri var. navia of Conrad and Hall the name 
Gryphaea Rdmeri, in honor of its first discoverer, Mr. Fr. Romer. (Notes on the Cre¬ 
taceous and Carboniferous rocks of Texas, Proc. Bost. soc. nat. hist., vol. 8, p. 95.) 
