480 MESOZOIC TIME. 



westward to the Arctic seas, at the mouth of Mackenzie River, where- 

 beds of this period occur. 



This Cretaceous Mediterranean Sea spread westward among several 

 of the elevations of the Rocky Mountain summits ; and, in New 

 Mexico, it spread still farther westward, over the region of the Upper 

 Colorado, to or beyond the meridian of 113° W. In California, it 

 covered the region west of the base of the Sierra Nevada. 



By comparing the above map with that of the Archaean (p. 149), it 

 is seen that the continent had made great progress since the opening 

 of the Silurian age. But, as all this Cretaceous area was under Cre- 

 taceous seas, much was still to be added to the permanent dry land 

 before its completion. 



The great Interior Continental basin, which had been a limestone- 

 making region, for the most part, from the earliest period of the Si- 

 lurian, was still, in its southern part, — that is, in Texas, — continuing 

 the same work ; for limestones eight hundred feet thick were there 

 formed. To the north of Texas, where the waters were shallower,, 

 there appear to have been none of the Echinoderms, Corals, Orbi- 

 tolinae, etc., which were common in Texas. 



3. Foreign Geography. — The distribution of the Cretaceous beds 

 over other continents shows that the lands were to a great extent sub- 

 merged. The sea covered a large part of the region of the Andes, as 

 well as of the Rocky Mountains ; and large portions of both chains 

 were not yet raised into mountain-shape : the Alps, Pyrenees, and 

 Himalayas were partly under water, or only in their incipient stages of 

 elevation. Europe was mostly a great archipelago, with its largest 

 area of dry land to the north ; it resembled North America in the 

 latter point, while widely differing in the former. The Urals and 

 Norwegian mountains were the principal ranges of Europe, as the 

 Appalachians and the Laurentian heights of Canada and beyond were 

 in America. Western Britain was the high land of that region ; and,, 

 under its lee and that of other lands southwestward across the Chan- 

 nel, the new formations of eastern England and northern France were 

 in progress in deep waters bordering the German Ocean. 



4. Climate. — The geographical distribution of species indicates a 

 prevalence of warm seas in the northern hemisphere to the parallel of 

 60°, and in the southern to the Straits of Magellan. For the table on 

 page 476 shows that several species are common to Britain, Europe, 

 and either equatorial America, India, or the United States. The survey 

 of the life of the period, therefore, so far as now known, affords no 

 evidence of the existence of the present cool temperature in the waters 

 of the temperate zone. 



The corals of the Cretaceous beds in England may be those of cool 



