32 TRANSACTIONS OF THE [nOV. 24, 



The age of these vegetable remains is that of the Pre-glacial 

 Drift. Some of the species represented are still existing in the 

 present flora. 



The Pre-glacial Drift inconformably overlies the miocene 

 strata of Southern New Jersey. In fact, the Bridgeton Plant 

 Bed above described is over Miocene materials. It is then Pli- 

 ocene or yet more recent, I am inclined to regard the forma- 

 tion as later Pliocene or Pleistocene, mainly from the modern 

 character of the plants from Bridgeton, though these cannot be 

 regarded as absolute proof. Silicified wood occurs in the Pre- 

 glacial Drift in considerable abundance. I have examined sec- 

 tions of some of this, and they are of coniferous trees. It may 

 be that a more extended study of the fossil woods may shed 

 more light on this question. 



The Origin of the Materials composing the Pre-glacial 

 Drift. — It must be admitted at the present writing, that the 

 location of the rocks from which the pre-glacial gi-avel and 

 sand have been derived is not certainly determined. Professor 

 Cook has argued that inasmuch as there is no red shale nor 

 sandstone fragments in the formation, it cannot have come fi-om 

 the northwest, for to have been transported from that du*ection 

 it nuist have crossed thirty miles or more of Triassic red rocks, 

 and would certainly contain some fragments of these. In fact, 

 he concluded that it must have come from the southeast, and 

 thus from rocks now submerged in the Atlantic. The absence 

 of any known reefs of such rock, or of any indications of their 

 existence weigh heavily against this hypothesis, and it would 

 seem that some other explanation must be found. I am not 

 aware that up to the present time any other hypothesis has 

 been published regarding the origin of these materials. 



I will briefly refer to certain facts which may furnish clues 

 in the future study of the formation. 



(1) A large part of the gravel is evidently vein-quartz, and 

 thus must have come from crystalline or partially metamor- 

 phosed rocks. The former are known to exist along the junc- 

 tion of the Triassic and Cretaceous formations from New York 

 to Philadelphia, and further southwest. It would seem that 

 the crystalline rocks of the Highlands of New Jersey are too 

 far distant to have yielded much of the material, and this taken 

 with the difficulty of its having to cross the red Triassic strata. 



