FOSSIL PLANTS AS AN AW TO GEOLOGY. 373 



three species of plants characteristic of the lower Cretaceous, 

 and appears to find its closest resemblance in the older portion 

 of the lower Potomac. Professor Fontaine's results are summed 

 up as follows: "The Glen Rose or alternating strata, in which 

 the fossil plants are found, contain an abundant marine fauna, 

 from the evidence of which Professor Hill had concluded that 

 its age was Neocomian or basal Cretaceous. No fossil plants 

 had hitherto been found in the Comanche series, and the evidence 

 of its age was derived wholly from the animal remains. The 

 discovery of plants in it was, then, of special importance, for it 

 enabled us to compare the evidence of the plant-life with that of 

 the animal life. It is interesting to find so close an agreement. 

 This agreement adds one more proof of the value of fossil floras 

 in fixing the age of the strata in which they are found." 



The age of the strata exposed at Gay Head, on the western 

 end of Martha's Vineyard, has been the subject of discussion 

 and speculation by geologists for nearly or quite a hundred years, 

 and the question has only recently been settled. In general the 

 strata have been correlated with the similarly appearing strata of 

 Alum Bay in the Isle of Wight, the position of which is fixed as 

 middle Eocene. It is true that certain Cretaceous shells had 

 been found, but they were not in place, and so intermingled with 

 recent forms, that it was concluded that the age could hardly be 

 other than lower or middle Tertiary. As late as 1889 Professor 

 N. S. Shaler' decided, upon purely stratigraphic grounds, that 

 "this part of the Tertiary series is certainly of later Miocene or 

 Pliocene age. 



In 1890 Mr. David White visited Martha's Vineyard, and was 

 fortunate enough to find and collect a considerable series of fossil 

 plants from the strata in question. The results of this study ^ 

 showed beyond all doubt that they were of Cretaceous age, 

 many being identical with the plants of the Amboy clays of New 

 Jersey. "The Gay Head flora," Mr. White concludes, "indi- 



' Seventh Annual Report U. S. Geol. Survey, 1885-6, p. 332. 

 ^Cf. Am. Jour. Sci., Vol. XXXIX., 1890, pp. 93-101. 



