249] W. P. Woodring 51 



A single fragmentary valve of an indeterminable Spisula is 

 the sole representative of the Mactridae. Two of the three 

 species of Corbula, the only non-boring Myacea, are exceed- 

 ingly abundant. The unusually favorable conditions of pre- 

 servation are indicated by the presence of several fragile 

 boring Adesmacea. 



3. PHYSICAL CONDITIONS 



The student of recent marine faunas would consider with 

 undisguised suspicion an attempt to reconstruct environ- 

 mental conditions on the basis of the testimony furnished by 

 a single element in a fauna. Despite the lack of an intensive 

 census of a restricted shallow-water West Indian area, which 

 would be of inestimable value in projecting backward the fac- 

 tors that determined the assemblage of an Antillean Tertiary 

 fauna, the ensemble of Bowden pelecypods is such as to per- 

 mit the offering of certain considerations, some of which are 

 more or less obvious and even trite. 



Though it is a mere platitude to state that the fauna is 

 tropical, yet this facies is emphasized in a striking manner 

 by the development of certain groups and the absence of 

 others that are prominent in the Tertiary faunas of the south- 

 ern Atlantic Coast. The most prolific genera Area, Pecten, 

 Phacoides, Cardium, Tellina are characteristically tropical 

 or are represented only by sections or species that are con- 

 fined to low latitudes or there reach their maximum develop- 

 ment. According to the latest faunal lists only two of the 18 

 species that persist to the Recent at present range north of 

 Cape Hatteras the ubiquitous Anomia simplex d'Orbigny 

 and Divaricella quadrisulcata (d'Orbigny). Eight are re- 

 corded from Hatteras southward to the West Indies or Brazil ; 

 seven are confined to the area south of Florida and one species 

 is restricted to the tropical portion of the West Coast. Vir- 

 tually the same proportions obtain for a large number of 

 Recent species that closely resemble Bowden forms. 



The Areas reach their greatest importance in the warmer 



