THE COMAXCHEAN PERIOD. 133 



with their introduction there by sea currents from the western con- 

 tinent, than with an origin on the eastern continent, for they were 

 not there generally prevalent until the beginning of the Upper Cre- 

 taceous. 



The view that seems best justified at the present stage of 

 evidence is that the angiosperms developed on the old lands of the 

 eastern part of North America, and that until the close of the Lower 

 Cretaceous they had only spread westward as far as Kansas and the 

 Black Hills, northward as far as Greenland, and eastward to the coast 

 of Portugal, but not to Europe generally, nor to the western part of 

 North America, for they do not appear in the Kootenay or the Shastan 

 series. As the northeastern part of North America had long been land, 

 and has left no record of plant-life, there is nothing to indicate how 

 much earlier angiosperms may have begun their evolution there. 

 The Jurassic beds of the western part of the continent and of Europe 

 give negative evidence as to a dispersion earlier than the Cretaceous 

 period. 



In the most typical region on the Atlantic coast nearly half the 

 known 800 species of Comanchean age are angiosperms. They began 

 in marked minority in the lowest Potomac and increased to an over- 

 whelming majority in the uppermost beds. 1 The earliest forms are 

 ancestral, but not really primitive, and throw little light on the deriva- 

 tion of the angiosperms. While some are undifferentiated, the majority 

 bear definite resemblances to modern genera, and some (as Sassafras, 

 Ficus, Myrica, and Aralia), are referred to living genera, while others 

 are given generic names implying the similarity of the fossil leaves 

 to those of living plants (as Saliciphyllum, willow-like leaves, Qaerco- 

 phyllum, oak-like leaves, and analogous names for plants whose leaves 

 resembled those of the elm, walnut, maple, eucalyptus, and others). 

 To these were added, in the Amboy (N. J.) clays at the very close of 

 the period, figs, magnolias, tulip trees, laurels, cinnamon, and other 

 forms referred to modern genera, but not to modern species. The 

 cycadeans had dropped to an insignificant place, and the conifers and 

 ferns, while not equally reduced, were markedly subordinate to the 

 angiosperms. 



The land animals. — The aspect of the vertebrate life was inter- 

 mediate between that of the Jurassic and of the Upper Cretaceous, and 



1 Newberry, Mon. XXVI, U. S. Geol. Surv., 1895, p. 23. 



