If now we turn to the Cretaceous and Tertiary floras of Western America, as described by Lesquereux, Newberry, and Ward, we find in the lowest Cretaceous rocks known there until very recently--those of the Dakota group, which may be in the lower part of the Middle Cretaceous--a series of plants[96] essentially similar to those of the Middle Cretaceous of Greenland. To these I have been able to add, through the researches of Mr. Richardson and Dr. G. M. Dawson, a still earlier flora, that of the Kootanie and Queen Charlotte Island formations, as old as the Gault and Wealden. It wants the broad-leaved plants of the Dakota, and consists mainly of pines, cycads, and ferns; and only in its upper part contains a few forerunners of the exogens.[97] These plants occur in beds indicating shallow sea conditions as prevalent in the interior of America, causing, no doubt, a warm climate in the north. Overlying this plant-bearing formation we have an oceanic limestone (the Niobrara), corresponding in many respects to the European chalk, and containing similar microscopic organisms. This extends far north into the British territory,[98] indicating farther subsidence and the prevalence of a vast Mediterranean Sea, filled with warm water from the equatorial currents, and not invaded by cold waters from the north. This is succeeded by Upper Cretaceous deposits of clay and sandstone, with marine remains, though very sparsely distributed; and these show that further subsidence or denudation in the north had opened a way for the arctic currents, producing a fall of temperature at the close of the Cretaceous, and partially filling up the Mediterranean of that period. [96] Lesquereux, Report on Cretaceous Flora. The reader not interested in American details may pass over to the middle of page 213. [97] This flora has since been described in Virginia and Maryland by Fontaine, and has been recognised in Montana by Newberry. [98] G. M. Dawson, Report on Forty-ninth Parallel. Of the flora of the Middle and Upper Cretaceous periods, which must have been very long, we know something in the interior regions through the plants of Dunvegan and Peace River;[99] and on the coast of British Columbia we have the remarkable Cretaceous coal field of Vancouver's Island, which holds the remains of plants of modern genera, including species of fan palm, ginkgo, evergreen oak, tulip tree, and other forms proper to a warm temperature or subtropical climate. They probably indicate a warmer climate as then prevalent on the Pacific coast than in the interior, and in this respect correspond with a meagre transition flora, intermediate between the Cretaceous and Eocene or earliest Tertiary of the interior regions, and named by Lesquereux the Lower Lignitic. [99] _Trans. Royal Society of Canada._