LOWER CRETACEOUS FORMATIONS AND FAUNAS 581 
approximately their present positions, since the European 
localities are respectively several degrees farther north than 
their American analogues, corresponding to the position of 
isothermal lines on opposite sides of the Atlantic at the present 
time. This was one of the first attempts to establish climatal 
zones at such an early period, as it was published even before 
von Buch’s* generalization that the absence of Cretaceous faunas 
in the polar regions is due to the climatic conditions of that 
period. In Neumayr’s studies of Mesozoic climates use was 
made of the difference between the Cretaceous faunas of New 
Jersey and Texas, and it has recently been cited by Kayser? and 
by J. Perrin Smith.3 There is some evidence of the existence of 
climatal zones in the Cretaceous and even earlier in Mesozoic 
time, but Roemer’s original examples should no longer be cited 
as proof, for it is now known that the faunas Roemer compared 
were not contemporaneous, the base of the marine Cretaceous 
beds in New Jersey being somewhat newer than the uppermost 
horizon that furnished the fossils he described from Texas. If 
he had made his comparisons with the Ripley fauna, which 
occurs near the top of the Texan Cretaceous and only a few 
miles east of the beds studied by him, Roemer’s conclusion 
would probably have been very different, for a very large per- 
centage of the species are identical with the New Jersey forms, 
and there is nothing suggestive of a warmer climate.t The 
Upper Cretaceous faunas of the Atlantic and Gulf border regions, 
when comparison is made with strictly homotaxial zones, are 
remarkably uniform along the whole coast from Texas to New 
Jersey. 
The correlated faunas of the Rocky Mountain region and 
the great Plains show much greater differences when compared 
with the faunas just mentioned, and these may reasonably be 
tVerbreitung und Grenzen d. Kreidebildungen. Verhandl. des Naturhist. Vereins 
d. Preuss. Rheinlande u. Westphalien, Bd. 7, pp. 211-242. 
2Text-book of Comparative Geology, translated by Lake, p. 283, Lond., 1893. 
3 Jour. of GEOL., Vol. III, p. 485, Chicago, 1895. 
4See WHITFIELD; Bull. Am. Mus. Nat. Hist., Vol. II, 1889, pp. 113-116 and 
WHITE, Bull. U. S. Geol. Surv., No. 82, pp. 84, I11. 
