LOG Upper Cretaceous Fauna, from Tennessee [298 



sand extends further southward and at Sand Hill is over- 

 lain by calcareous sediments containing an unstudied fauna 

 of probably 50 species. Three miles farther southwest there 

 are non-fossiliferous gypsifeous clays at the base of the Eipley. 

 Overlying the variable Coon Creek horizon is a thickness 

 of ferruginous and micaceous Eipley clays which extends in 

 a belt across the county. These sediments contain a sparse, 

 dwarfed fauna of a few pelecypod genera such as Cardium, 

 Cyprimeria, Pecten, etc., none of which are as much as one- 

 half inch in maximum diameter. Gastropods, cephalopods 

 and large massive bivalves such as Exogyra or Gryphaea -are 

 absent. Evidently conditions were unfavorable for molluscan 

 life where these deposits were formed. Above this is the non- 

 fossiliferous McNairy sand, and overlying that is the classic 

 fossiliferous Owl Creek horizon. Thus the evidence seems 

 to show that there were local areas where conditions were 

 very favorable for rapid development of life, while other 

 regions were not suited to the growth of marine organisms. 

 There were probably local biological provinces which favored 

 the development of local faunas. This may be observed in 

 a comparison of the Owl Creek and Coon Creek faunas. Al- 

 though these localities are within sixty miles of one another 

 and in the same formation, the two faunas have a distinctly 

 different aspect. Very many of the species are different yet 

 many are identical. There are a number of genera from 

 each locality not common to the other. At Owl Creek the 

 percent of bivalve species is greater than that of the uni- 

 valves, while at Coon Creek the fauna is striking for the 

 predominance of gastropod species. The Cephalopod SpJie- 

 nodiscus has not been found at Coon Creek while at Owl 

 Creek it is represented by two species. As has been stated 

 above the Owl Creek horizon is stratigraphically above the 

 Coon Creek beds so there should be some differences in the 

 faunas due to age but it is a question whether there should 

 be such a striking difference in assemblages from the same 

 formation located so near each other if such conditions as 

 local biological provinces had not existed. It seems reason- 



