Ptrmian Formation of Texas. 125 
Heretofore it has been impracticable to say whether the upper 
limit of the Carboniferous system in North America is complete or 
not. For example, none of the reputed Triassic strata, which occur 
in various parts of the continent, have been found in such relation 
to the reputed Permian as to indicate that there was continuous 
sedimentation from the one formation to the other ; nor have those 
Triassic strata been found to contain any conclusive palaeontological 
evidence of their immediate succession to the Permian. Indeed, 
as regards the remains of invertebrate life, the existence of any 
Triassic strata in North America rests upon comparatively slight 
evidence ; slighter, indeed, than it might have seemed to be before 
the discovery of Triassic types associated with well-known Carbon- 
The conflicting character of a part of the evidence afforded by 
the reputed North American Permian as to its age has already 
been shown, but there is an important case of want of harmony of 
different portions of certain accepted paleontological evidence that 
deserves mention. In Professor Cope's systematic catalogue of the 
Permian vertebrate fauna of North America," he shows that it has 
been discovered mainly in two limited districts, one in eastern Illi- 
nois and the other in Texas. His catalogue also shows that of the 
76 species enumerated, not one, and of the 32 genera only five, are 
common to the two districts. He also states that "the Permian 
vertebrate fauna of Illinois and Texas exhibits close parallels, but 
not yet generic identity on this continent."^- 
On the contrary, the marine invertebrates which characterize the 
North American Coal-measures, a part of which usually range up 
into the reputed Permian, are widely distributed on this continent, 
erous series ; seeminjj thereby to imply that the series includes an inseparable 
equivalent of the Permian, as well as the remainder of the system. 
" The Triassic character of a part of the Permian fauna of Texas has been suf- 
ficiently stated, but it is also true that certain Carboniferous types occur in the 
Meekoceras beds of southeastern Idaho. Besides this, those beds appear to have 
an intimate stratigraphical relation with the characteristic Carboniferous strata be- 
neath them. Add to these facts the further one that types similar to those which 
have been relied upon in referring the Idaho beds to the middle Trias, also occur 
in undisputed Carboniferous strata, and it seems possible that those reputed Trias- 
sic beds ought to be referred to the Permian rather than to the Trias. 
'" Trans. Am. Philos. .Soc. vol. XVI, pp. 285-288. 
