40 Environment of Tertiary Marine Faunas [238 



from the adult, the number of specimens is given and the data 

 upon depth, temperature, salinity, etc., is complete and accu- 

 rate. The bathymetric distribution of most of the southern 

 stations is unfortunate for those interested in determining 

 the limits in depth of the littoral fauna. Very little shore 

 dredging has been done and there are very few records from 

 less than 10 fathoms. A number of unusually rich hauls were 

 made off Hatteras between 15 and 25 fathoms. The 49 and 

 63 fathom stations include in addition to the native fauna a 

 considerable number of young or more or less worn shells 

 referrable to the more abundant species in the lesser depths 

 but in the great majority of records these fortuitous shells 

 have not been isolated. However, the general relationships 

 which come out of an interpretation of the recent elements in 

 the fossils faunas are probably true, even though the data 

 upon which the results are based is woefully inadequate. 



Five formations have been recognized in the Miocene and 

 Pliocene of Virginia and North Carolina, the Calvert, St. 

 Mary's and Yorktown in Virginia and the Yorktown, Duplin 

 and Waccamaw in North Carolina. The Yorktown and Du- 

 plin were probably, for the most part, synchronous though 

 laid down in separate basins. Approximately 65% of the 

 species common to the Calvert and Recent faunas have been 

 reported from north of Hatteras, the limit of range of many 

 of the northern and of the southern forms; 54% of the St. 

 Mary's; 46% of the Yorktown; 35% of the Duplin, and 

 36% of the Waccamaw. Factors other than temperature have 

 modified somewhat the figures for the Duplin and Waccamaw, 

 for there is no reason to suppose that the Waccamaw sea was 

 not quite as warm as the Duplin. 



The break between the late Oligocene and the early Mio- 

 cene in the Southern Atlantic states is one of the sharpest in 

 the stratigraphic succession of the Cenozoic. The Oligocene 

 has not been recognized either in Virginia or North Caro- 

 lina but the early Miocene fauna is similar in general charac- 

 ter wherever it occurs along the East Coast. Twenty species 



