Bulletin 28 160 



spread in the Murfreesboro, Yorktown and Duplin stages. 



The mactroid Mulinia conge sta is an upper Miocene species 

 not recorded from the St. Mary's or older beds. It is by far the 

 commonest pelecypod of the Murfreesboro stage. 



Amongst the gastropods, the Maryland Busycons such as 

 B. coronatum and fusiforme are entirely lacking, their place being 

 taken by the larger and more modern species as B. maximum 

 and incile. 



The Calliostomas, the smaller Nassas, Turritellas, all offer 

 the same evidence. The whole fauna being distinctly of an up- 

 per Miocene type. 



Since the Murfreesboro stage is older than the Yorktown, it 

 is natural to expect that it should exhibit closer relation with the 

 St. Mary's than is the case with the Yorktown. 



Several species of Isocardias are abundant in the Maryland 

 Miocene but are rare or entirely absent in the Yorktown and 

 Duplin stages. They are well represented in the Murfreesboro 

 and often extremely abundant in certain clay beds. 



The geologic range of Melina maxillata is interesting, and 

 the presence of this species associated with an upper Miocene 

 fauna is the best criterion for the field identification of the Mur- 

 freesboro stage. This species is very abundant in our Lower 

 Miocene, especially in the Choptank. It continues through the 

 St. Mary's into the Murfreesboro and there sometimes equals, 

 as far as number of specimens is concerned, its former import- 

 ance in the Choptank. The species, so far as my knowledge 

 goes, is entirely lacking from the Yorktown and Duplin stages. 



The Maryland Miocene 



Since the Murfreesboro stage has frequently been correlated 

 directly with the St. Mary's or older beds, a brief review of the 

 more important paleontological characteristics of the Maryland 

 Miocene may be of interest. 



In many respects, the Miocene of Maryland is a unit, its dif- 

 ferent parts being more intimately related to each other than to 



