34 Reviews — Outlines of Geologic History. 



annelid trails indicate that this phase of the fauna was also strongly- 

 developed. Stratigraphically, this fragment of what must have been- 

 a large fauna occurs over 9,000 feet beneath an unconformity at the 

 base of the upper portion of the Lower Cambrian in northern 

 Montana". 



In support of his contention that the Cambrian faunas were 

 profoundly influenced by their environment, Mr. Walcott observes 

 that in the restricted waters of the Lower Cambrian the known 

 Brachiopods (of the entire world) were represented by twenty genera 

 and seventy-five species, whereas in the expanding seas of the 

 Middle Cambrian thirty-one genera and 243 species are known to 

 have existed. 



The physical and faunal evolution of North America during 

 Ordovician, Silurian, and early Devonian time is dealt with by 

 Professor A. W. Grabau ; and he is followed by Mr. Stuart Weller, 

 who discusses the correlation of the Middle and Upper Devonian 

 and the Mississippian faunas of North America. In these articles the 

 distribution of the faunas, the invasions of forms from other areas, 

 and their dependence on sedimentary conditions are discussed ; and 

 Professor Grabau describes the effects of ' regressive overlap ' or 

 ' off-lap ' when the area of sedimentation was lessening. Mr. Weller 

 remarks that " All questions in correlation become progressively more 

 complex as the territory occupied by the faunas under consideration 

 is extended " — their history, in fact, has to be considered biologically, 

 geographically, and geologically. 



Mr. G. H. Girty writes on the Upper Carboniferous or Pennsylvanian, 

 and in the course of his essay observes that "The Upper Carboniferous 

 faunas of Western North America have a facies markedly different 

 from those of the eastern part, and are closely comparable to the 

 corresponding faunas of Asia and Eastern Europe". The author 

 doubts whether the Kansas Permian and the Russian Permian were 

 contemporaneous; the weight of evidence, as presented by invertebrate 

 palaeontology, appears to him to favour the view of the pre-Permian 

 age of the Kansas deposits. 



Mr. David White discusses the evidence of the Upper Palaeozoic 

 floras, their succession and range, and the changes brought about by 

 great diastrophic movements. Thus the extensive orogenic movements 

 in Europe stimulated the evolution of the Permian flora, whereas "in 

 the Appalachian trough, where environment was but little affected 

 by orogeny, and where sedimentation wrts- uninterrupted, there is only 

 gradual change, many of the Stephanian [Carboniferous] types 

 persisting far up in the Dunkard formation" or Permian of South- 

 western Pennsylvania. The plants do not appear to differ in kind, 

 whether found in the grey limestone-bearing strata or in the red 

 rocks that are nearly devoid of limestones. 



The faunal relations of the early air-breathing vertebrates form the 

 subject of an essay by Dr. S. W. Williston, who discusses the 

 evidence of continued intermigration of land animals between 

 the eastern and western continents. Then follow a series of articles 

 on the succession and distribution of later Mesozoic Invertebrate 

 faunas in North America, by Mr. T. W. Stanton ; on the succession 



