334 E. C. CASE-^CLIMATIC ENVIRONMENT OF EXTINCT ANIxMALS 



first group belong all the suggestions which come from the animals them- 

 selves, with all the hints that come from their various adaptations and 

 specializations. To this is added the important evidence of the associa- 

 tion of various plants and animals in the same bed and in the same 

 locality. In the second group belong the sediments of the inclosing beds, 

 with the facts of their physical condition and mode of deposition, the 

 facts of their original or altered composition, the nature of the cementing 

 material, and the possible changes subsequent to deposition. 



The first point in any determination is the recognition of the fact that 

 most vertebrate fossils lie buried in sediments which do not represent 

 directly the normal habitat of the animals. The sea-bottom was not the 

 habitat of the free swimming forms, nor were the muds and sands of a 

 swamp, a lake, or a river bottom the home of terrestrial animals. Only 

 for such forms as normally lived in the actual area of deposition, as 

 bottom-dwelling or palustral forms, can subaquatic sediments be inter- 

 preted as reflecting directly the climatic conditions during life. In al- 

 most every case the inclosing sediments have been transported from ■» 

 terrestrial or semi-terrestrial position and laid down again after more or 

 less profound changes due to erosion and transportation. 



Inokganic Ckiteeia: Ciiaractek or Sediments 



Primarily, then, the worker must determine whether the remains lie in 

 sediments which directly reflect the environment or whether they are 

 sediments which have been derived and transported from the area of the 

 environment, and they can only be correctly interpreted after the changes 

 inherent in such derivation and transportation have been reckoned with. 



The changes which occur in derived sediments belong in the category 

 of inorganic criteria. It is, perhaps, not usually expected that the stu- 

 dent of animal morphology will be familiar with the tenets of physiog- 

 raphy, or that he should be conversant with the principles of metamor- 

 phism, but the paleontologist of today is rarely so limited in his outlook 

 that he is content with the mere description of new forms or with bare 

 anatomical comparisons. Eather he is a paleogeographer, Avho acts on 

 the principle that geography is the study of the response of the organism 

 to its environment, Avhether he subscribes to that definition or not. He 

 is much more interested in the factors Avhich influenced the evolution of 

 an animal or a group than he is in the direct evidence of evolution. For 

 one, the author has found it Avise to keep Van Ilise's Treatise on Meta- 

 morphism and CUark's Data of Geochemistry within short reach Avhen he 

 is engaged on a problem of vertebrate paleontology, and he has found it 

 equally wise to have some good treatise on j^hysiography close to his hand. 



