1 88 T. W. STANTON 



between the Arctic and Pacific Oceans. The closing of these con- 

 nections would modify the currents, change the climate, and permit 

 immigration of fauna! elements from other areas without any other 

 geographic changes.' 



Comanche faunas. — The whole of the Comanche series is here 

 treated as Lower Cretaceous, because in the Texan area the top of 

 the Comanche is the only natural and satisfactory major plane of 

 division in the Cretaceous. Stratigraphic, lithologic, and paleonto- 

 logic studies all lead to the same conclusion. Many European 

 paleontologists believe that the upper or Washita portion of the 

 Comanche is of Cenomanian age and hence referable to the Upper 

 Cretaceous of European standards and the IMexican geologists, while 

 adopting this view, advocate for their country a threefold division of 

 the Cretaceous and call the upper part of the Comanche, including 

 the Fredericksburg and Washita groups, Middle Cretaceous. These 

 varying views as to the classification and correlation of the formations 

 are not important in the present discussion of the succession and 

 distribution of the faunas which are grouped under the term Comanche. 

 These faunas show many facies varying from time to time and from 

 place to place. There are littoral faunas, reef faunas, and deeper- 

 water faunas, but the reef facies is perhaps the most striking and 

 characteristic. And yet these different facies are all so intimately 

 connected either by common species or by stratigraphic relations that 

 it is appropriate to speak of the Comanche fauna as a whole. When 

 the Comanche fauna is examined either as a whole or in detail it 

 proves to be very similar to the Cretaceous fauna of the Mediterranean 

 province in southern Europe, and it is strikingly contrasted with the 

 Shasta fauna of the Pacific coast, although the Comanche area in 

 Mexico closely approaches the present Pacific coast throughout that 

 country. On a previous occasion I have called attention to the charac- 

 ter of the differences between the Shasta and Comanche faunas.^ 

 They are not made up of related forms differing specifically, but they 

 consist mainly of different classes of animals so that they present 



I See Von Koenen Festschrift, p. 433, where J. P. Smith has suggested that periodic 

 opening and closing of these connections are sufficient cause for the changes in Meso- 

 zoic and later faunas of the Pacific coast. 



^ Jour, of GeoL, Vol. V (1897), p. 608. 



