Smith.] 232 [Oct. 2, 



Replacement of Limestones hy Cocd-hearincj Formations in Western 



Euroiie. 



On tracing the Upper Carljoniferous deposits of the Ural region to- 

 wards the west, we find the limestones thinning out, and the Coal mea- 

 sitres and Culm formations taking their places ; we find also that the 

 transgression of marine on terrestrial deposits takes place from the east, 

 just the reverse of Avhat is seen in America. 



Land Areas in the West. 



It is not thought that the Pacific Carboniferous sea was an un- 

 broken expanse of water in western America ; on the contrary there 

 are many evidences of large isolated land areas and archipelagos. 

 Dr. Joseph Le Conte* has argued that the Basin range, during much 

 of Paleozoic and Mesozoic time, was a continent, oflf the western shores 

 of which the sediments that afterwards became the Sierra Nevada and 

 Coast range w^ere laid down. Clarence Kingf thought that the great 

 thickness of Paleozoic littoral deposits in the Great Basin region proved 

 the existence of a large body of land further west ; he thought that the 

 eastern shore of this continent was in Nevada, and east of this stretched 

 the Carboniferous sea, which covered all but the island chain of the 

 llocky Mountain region. King:]: further concluded that the Carbonifer- 

 ous in California, west of the old shore line, indicated shallow bays that 

 permitted the western extension of the upper Paleozoic deposits, while 

 the bulk of them was stopped by the bold coast. There are evidences 

 of land areas in the Eocky mountains, Wahsatch mountains. New Mex- 

 ico, and Nevada, but from the facts now known it seems more probable 

 that these were large islands or archipelagos, rather than continents. 



The Permtan Pacific Ocean. 



The outlines of the great western ocean can be traced in Permian 

 times also, but with much more circumscribed limits. Open-sea deposits 

 of this age are known in Texas, in the Salt range, on the west slope of 

 the Urals, on the island of Sicily, and in scattering places in Central 

 Asia. In all these the genera are nearly the same, except that the Ar- 

 eestes types are confined to the more southern regions. This similarity 

 indicates plainly a connection of these deposits. 



Suessg argues that the open-sea Permian fauna wandered in from the 

 south, and that the Mesozoic types of ammonites were foreign to the 

 northern regions. Karpinsky, || on the contrary, holds that they were 

 autochthonous, at least in the Ural region, since he could trace the de- 

 scent of all the ammonites except the Popamwcrata from goniatites that 



* American Journal of Science, iii, Vol. 16, p. lOS. 



t U. S. Gcol. Explor. Fortieth Parallel, Vol. i, p. 5o-l. 



:J: Oi>. at., p. 5S5. 



§ Antlitz der Erde, ii, p. 316. 



1! Ammoiieen der Artinsk-Stnfe, p. 86. 



