MUSEUM OF COMPARATIVE ZOOLOGY. 95 



North American coast was also not far from its present altitude. These 

 fragments lie at the height of about 150 feet above tide-water ; the most 

 elevated point at which I have traced the Tertiary deposits of the Gay 

 Head series is about the same height. Taken together, these two sec- 

 tions afford interesting evidence of the existence of the shore line close 

 to the present coast in two remote stages of the earth's history. 



The occurrence of Cretaceous deposits in this part of New England is 

 particularly interesting, for the reason that it indicates the former exten- 

 sion of the deposits of this age to points much farther north than they 

 have hitherto recognized on the eastern versant of the continent. Hith- 

 erto, no beds of Cretaceous age have been known on the Atlantic coast 

 north or east of New Jersey. This new locality establishes the existence 

 of such beds about 100 miles farther north, and about 200 farther east 

 than those which occur in the New Jersey area. 



The fact that the Martha's Vineyard Cretaceous material was appar- 

 ently deposited near a shore line, appears to indicate that the Cretaceous 

 section, at least that part which belongs in this particular horizon, never 

 covered the general surface of New England. Therefore we cannot 

 fairly attribute to erosion the absence of this portion of the Mesozoic 

 deposits in the New England area and the region to the northward. It 

 seems to me more likely that these beds were never deposited on that 

 portion of the continental surface. 



Palaeontology of the Martha's Vineyard Cretaceous. 



Although there can be hardly any question as to the general geologi- 

 cal position of the beds whence these fossils were derived, their precise 

 place in the section is not readily determinable with the material at 

 hand. As will be seen from the appended figures of fossils, the remains 

 are very imperfectly preserved, revealing the existence of four species 

 which are characteristically Cretaceous in their aspect. The species, 

 however, differs so far from that which has been found in more southern 

 portions of the continent that no sufficient identification of the particular 

 horizon is possible. 



The most abundant fossil is the ExogjTa, shown in Figs. 19 and 20 of 

 Plate II. The specific differences between the several species of Exo- 

 gyra are rarely if ever sharply defined. The Martha's Vineyard form 

 appears to be sufficiently distinct from any others which have been de- 

 scribed to warrant the application of a new specific name. So far, no 

 distinct Exogyras have been found above the horizon of the Cretaceous 



