283] B. Wade 85 



of Molluscoidea of the Class Bryozoa; 1 genus of Echinoder- 

 mata of the Class Echinoidea ; 2 of Vermes ; and 1 of Coelen- 

 terata of the Class Anthozoa. The Mollusca, however, are by 

 far the most abundant. In this group there are 49 genera 

 and 110 species of Pelecypoda; 2 genera and 3 species of 

 Scaphapoda; 60 genera and 120 species of Gastropoda; 4 

 genera and 7 species of Cephalopoda. 



It has been estimated that the Eecent east coast Molluscan 

 fauna of the Middle Atlantic States includes more than 500 

 species, and there is no reason to suppose that the Upper Cre- 

 taceous faunas were materially less prolific. On the contrary, 

 the seas were warmer and conditions more favorable to mollus- 

 can life, so that probably not more than one-half the entire 

 fauna has been discovered. 



The Coon Creek fauna flourished near the head of the 

 Mississippi Embayment and in about the same latitude as the 

 Middle Atlantic States. It was probably in the same general 

 climatic zone of the Cretaceous, so that any estimate of the 

 east coast fauna should hold for the northern part of the 

 Mississippi Embayment as well. The evidence afforded by 

 the Coon Creek material shows that the above estimate is not 

 overdrawn but probably conservative. The extent of the 

 undescribed fauna is indicated by the fact that four days col- 

 lecting at Coon Creek has yielded in the Mollusca alone over 

 100 new species, three new subgenera and eight new genera. 



The families and genera with the number of species in each 

 are as follows (a preliminary list made May, 1916) : 



CLASS PELECYPODA 

 Order Prionodesmacea 



Nfcculidae. Nucula 3 species 



Ledidae. Leda 2 species 



Yoldia 1 species 



Parallelodontidae. Nemodon 3 species 



Cucullaea 4 species 



Arcidae. Area 4 species 



Glycymeris 2 species 



Axinea 1 species 



Postligata 1 species 



