299] B. Wade 101 



able to conclude from a study both of the sediments and the 

 faunas and their distribution that, in this part of the Mis- 

 sissippi Embayment of the Ripley Sea, there were certain 

 restricted areas, that were especially favorable for the growth 

 of Mollusca. These areas were separated from one another 

 by regions, as the sediments show, not so favorable for marine 

 life and such regions as served to hinder free migration from 

 one province to another. In these isolated " places of much 

 life" variations took place due to biological and physical 

 conditions. Environmental changes were constantly taking 

 place due to shift and sinuosity of strand-line and change 

 in character of sediments. In many provinces the faunas 

 were destroyed entirely, in places some survived longer and 

 were dwarfed, favorable places were crowded with great 

 hordes and here evolutionary processes were most active. 27 



27 During the past winter, after the above preliminary account of 

 the Coon Creek fauna was written, the writer has been engaged in a 

 systematic study of the Gastropoda of this fauna in preparation of a 

 dissertation to be submitted to the Board of University Studies. A 

 few days collecting at Coon Creek during the summer of 1916 added 

 many excellent and interesting specimens to the collection and 

 the study of this material, together with that assembled in 1915, has 

 resulted in the recognition of about 75 genera and 140 species of 

 gastropods alone. About two-thirds of these are new species, as only 

 about 45 species of univalves were previously known from the Cre- 

 taceous strata of the Eastern Gulf Region, and of this number only 

 about 10 had been recognized in the State of Tennessee. It is proba- 

 ble that the locality is not exhausted as yet, and that further col- 

 lecting, which is planned for the summer of 1917, will yield a few 

 additional species of Gastropoda. 



