HACKBERRY STAGE OF THE UPPER DEVONIAN. 1 97 



Spirifer whitneyi Hall 



Spirifer hungerfordi Hall 



Athyris minutissima Webster 

 Mollusca 

 Pelecypoda 



Glossites sp. 



Grammysia(?) sp. 



Paracyclas sabini White* 



Paracyclas validalinea Vv^ebster 

 Gastropoda 



Platyostoma mirum Webster 



Platyostoma pervetum Welster 



Platyostoma sp. 



Platyostoma n. sp. 



Naticopsis rara Webster » 



Turbo (?) strigullata Webster 



Turbo (?) incerta Webster 



Holopea tenuicarinata Webster 



Cyclonema brevilineata Webster 



Cyclonema subcrenulata Webster 



IV. — The Age and Relationships of the Hackberry Stage. 



In section I of this paper there is given a summary of the age 

 and equivalency of the Hackberry beds; it is not necessary to 

 review this here. The two important questions are: (i) Is there 

 any described equivalent of the Hackberry Stage? (2) What claims 

 to the rank of stage can be advanced for the formation? 



The first question can be answered with a^decided negative. 

 Calvin, interpreted the fauna of the Independence Formation of 

 Iowa as the predecessor and direct ancestor of the Hackberry Fauna. 

 This interpretation, however, was based on a very small numter of 

 species, and it is doubtful if some of these can be satisfactorily 

 referred to both formations. 



Clarke' saw a considerable relationship between the Hackberry, 

 Independence, and High Point faunas. His conclusions, however, 

 were drawn, as shown in the. table given by him, from but a small 

 fraction of the bryozoan, brachiopod and mulluscan faunas of the 

 Hackberry, the -total number of species from the three formations 

 which were included in tl e talkie being forty- three. Aside from 

 'f Bulletin 16, U. S. G, 3-; PP- 74-76. 



