50 Pelecypods of the Bowden Fauna [248 



furnishes half of the species distributed among eight sections. 

 Two phacoidean elements, Lucinisca and Miltha, as well as 

 the genus Lucina, are absent. The Codakias and Myrtaeas 

 are abundant and well-developed. The Divaricellas are indi- 

 vidually numerous, whereas the Diplodontas are, as usual, 

 represented by a small number of individuals. 



In contrast to the richness of the lucinoids is the meager 

 representation of the Leptonacea. The entire superfamily 

 includes but four species segregated into three genera and as 

 many families. Furthermore, the four species are represented 

 by only six valves, two of which belong to the rarely encoun- 

 tered subgenus Basterotia of the genus Anisodonta. 



Among the larger groups is the genus Cardium, represented 

 by seven sections and eleven species. The sections are such 

 as are found in any tropical or sub-tropical mid-Tertiary 

 American fauna, but Cerastoderma and Papyridea are not 

 included. The Trigoniocardias, which are peculiar to the 

 mid- American region, are a conspicuous element; indeed, a 

 species of this section is the most abundant bivalve in the 

 fauna. 



The eight veneroid genera are divided among the sub- 

 families Meretricinae, Venerinae and Geminae. Chione is 

 the most abundant with regard to both the number of species 

 and individuals. Parastarte, represented by a single valve, 

 has heretofore not been reported outside of the Floridian 

 region either recent or fossil. The genus Tivela is not in- 

 cluded in any of the Tertiary faunas of the North American 

 mainland. An interesting form comparable to Cooperella in 

 dentition is placed in a new section of that genus. Only two 

 species of Cooperella are known, a Recent species from the 

 west coast of North America and another from the late Mio- 

 cene of the Atlantic Coast. 



The genus Tellina includes 15 species, distributed among 

 6 sections. Angulus has the largest number of species, but 

 the most abundant forms are found under Merisca and Moe- 

 rella. Among the Macomas is a typical Cymatoica. The 

 remaining Teleodesmacea are scattered among several groups. 



