428 PROCEEDINGS OF THE ACADEMY OF [1898. 



can be traced westward along the James River some eighty miles 

 or more to Richmond, Va., and after a careful study and analysis of 

 the contained mollusks and diatoms the conclusion before stated has 

 been reached that both the macroscopic and the microscopic fossils 

 indicate a mechanical mixture of the Miocene and a comparatively 

 recent fauna and flora 9 the Miocene forms having been contributed 

 and brought down by erosion from the broad and somewhat higher 

 and gradually rising Miocene belt to the westward, while the more 

 recent forms lived and were deposited as the bed was laid down in 

 a more recent geological time. 



If we accept the conclusions of all the authorities we have quoted 

 who have studied the Dismal Swamp deposit, we should have to re- 

 fer this bed unequivocally to the Pliocene period. The writer, how- 

 ever, cannot resist inferring from the scantiness of Miocene fossils, 

 which, as already noted, he views as mechanically introduced — 

 from the wide range of many of the Pliocene mollusks, extending 

 down to the present time — from the very decidedly recent aspect of 

 many other shells — and from the even more decidedly recent aspect 

 of some of the diatoms, a more recent date for the bed, and therefore 

 considers that it cannot belong to a period earlier than the latest 

 Pliocene, and that it may, indeed, even belong quite within Pleisto- 

 cene time. 



Specimens of all the mollusks listed from the Dismal Swamp 

 Canal have been presented to the Academy of Natural Sciences by 

 M. Homer, and are now arranged in its paleontological collection, 

 while strewn mounts of the diatoms have been deposited in the cab- 

 inet of the Biological and Microscopical Section by the author. 



9 Diatoms are now generally regarded as belonging to the plant kingdom. 



