140 THE INTERPRETATION OF THE PALEONTOLOGICAL CRITERIA 



lustrations since the marine forms of these two localities indicate very 

 different conditions from those now existing in the neighboring estuaries. 

 An even more striking locality containing marine fossils, although they 

 are not as numerous, is found in the valley of the Patapsco river near 

 Baltimore, not far from the ancient shore-line of the Talbot sea, and well 

 up the present estuary of the Chesapeake Bay, where the water is now 

 nearly fresh. That the greater part of this great area was covered in 

 Talbot time by much more highly marine waters is therefore clearly ap- 

 parent. 



In addition to the purely marine forms there are others of fresh- water 

 habitat, which evidently lived in ponded estuaries near the close of Tal- 

 bot time. Such are found at Bodkin Point near the mouth of the Pa- 

 tapsco river, where beds of dark-colored Ta]bot clay bear numerous casts 

 of indeterminable Unios similar in character to those found at the 

 famous Fish House locality in New Jersey, which Dr. Shattuck, on 

 physical grounds, has already correlated with the Talbot formation. 



The few land vertebrates found in the Talbot formation, although in- 

 teresting from the standpoint of their general geographical distribution, 

 are of little aid in the interpretation of the local deposits. The localities 

 are so few in number and furthermore the forms have been entombed 

 under such exceptional conditions as to raise some question regarding 

 their exact age, although they could not have antedated Talbot time and 

 may well have been of very late or even post Talbot age. 



The plants have been found at a number of localities in southern Mary- 

 land, a considerable assemblage of forms having been collected from both 

 the Sunderland and Talbot formations. As all of the Pleistocene forms 

 present so strong a modern aspect, being for the most part of living 

 species, they are of little aid in differentiating the Pleistocene into its 

 several divisions. It is evident that the formations so clearly marked 

 physically, represent relatively short time intervals when compared with 

 the Tertiary epochs which preceded them. Even the latter, which on 

 physical grounds afford evidence of much greater duration, contain great 

 numbers of forms in common, some of which are even found living to-day. 



