188 PHYSIOGRAPHY AND GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



somewhat generalized well records seems to be considerably more than 100 

 feet thick. Part of this thickness may represent the seaward portions of 

 the earlier Pleistocene formations that were not destroyed before the Talbot 

 was deposited. This variability in thickness is in part also explained by the 

 uneven surface upon which the formation was deposited. The proximity of 

 certain regions to mouths of streams during the Talbot submergence also 

 accounts for the increased thickness of the formation in these areas. 



Stratigraphic relations.- — The Talbot rests unconformably in different 

 portions of the region upon various older formations of Cretaceous- 

 Tertiary age. It doubtless occasionally rests upon some remnants of the 

 Lafayette, Sunderland, or Wicomico formations, although as yet no posi- 

 tive evidence has been found to indicate such relations to the older Pleis- 

 tocene formations. In all the subaerial portion of the Coastal Plain the 

 Talbot formation where present forms the surface material except where 

 covered by Recent deposits of sand (sand dunes) or humus. In the sub- 

 marine portion the Talbot apparently dips beneath the Eecent terrace now 

 in process of formation. 



Paleontologic diameter. — The fossils thus far reported from the Talbot 

 deposits in Virginia consist chiefly of marine shells from the eastern por- 

 tion of the Dismal Swamp and of plant remains found in swamp deposits 

 at many points. 



Miss J. A. Gardner has determined the following molluscan forms col- 

 lected from the Talbot deposits of the Dismal Swamp canal between mile- 

 posts 15 to 16. 



Nucula proxima Say. 

 Area transversa Say. 

 Area ponderosa Say. 

 Abra aequalis Say. 

 Divarieella quadrisulcata d'Orb. 

 Venericardia trideniata Say. 

 Ostrea virginica Gmelin. 

 Venus mercenaria (Linne). 

 Tellina tenera Say. 

 Cumingea tellinoides (Conrad). 

 Ensis directus (Conrad). 

 Mulinia lateralis Say. 

 Corbula eontracta Say. 



Marginella limatula Conrad. 

 Polynices duplicatus (Say). 

 Crepidula plana Say. 

 Crepidula fornieata (Linne) 

 Urosalpinx cinereus ( Say ) . 

 Evpleura caudata (Say). 

 Columbella liinata (Say). 

 Ilyanassa obsoleta (Say). 

 Nassa trivittata ( Say. ) 

 Fulgur cunaUridaium (Linne) 

 Fulgur earica Gmelin. 

 Terebra disloeata (Say). 

 Tornatina canaliculata (Say). 



In addition to the preceding species Rangia cuneata (Gray) has been 

 found at Pope Creek and Newport News and Unio sp. on the Eappahannock 

 Eiver, II/2 miles below Port Eoyal. 



