March 12, 1897.] 



SCIENCE. 



417 



changes took place that produced an extensive 

 destruction of vegetal types and altered the en- 

 tire character of the flora. 



" The localization of the species of Potomac 

 angiosperms and their slight development, 

 as shown in the very few individuals that 

 in most cases represent them, indicate that 

 these forms are, comparatively speaking, 

 newcomers and precursors or ancestors of 

 forms destined to become the predominant 

 ones. This indication is confirmed by the 

 character of a number of the species. They 

 appear to be complex or comprehensive 

 types, uniting in one form features that in 

 the process of differentiation will later dis- 

 tinguish separate species. 



" We may then conclude that the Potomac 

 flora is not exactly like any known, hut on 

 the whole coincides most nearly with that of the 

 Lower and Middle Neocomian. If this be 

 true, then, we find that in this flora the de- 

 velopment of angiosperms in considerable 

 numbers has been pushed back through a 

 long period of time." 



In view of the fact that Professor Marsh, 

 Mr. Gilbert and, to some extent, also Mr. 

 Hill, in discussing the age of the Potomac 

 formation, have referred to it as represent- 

 ing one definite epoch in the geological his- 

 tory of the Atlantic border, it does not 

 seem superfluous to emphasize to any extent 

 the fact which I have so prominently 

 brought forward in my paper on The Po- 

 tomac Formation,* and to which I also 

 called attention in my own contribution to 

 this discussion,! that the Potomac formation , 

 as I have defined it and as also defined by 

 Professor Marsh, including, as it does, the 

 Older Potomac beds of Virginia, the iron 

 ore belt, the purple clays, the white sands 

 and white rocks (Albirupean of Uhler, Ma- 

 gothy of Darton) , the Earitan and Amboy 



* Fifteenth Ann. Rept. U. S. Geological Survey, 

 pp. 307-397, Washington, 1895. 



t Science, N. S., Vol. IV., No. 99, Nov. 20, 1896, 

 p. 757. 



Clays of New Jersey, and the red micaceous- 

 clay shales of Staten Island, Long Island and 

 Block Island, as well as the variegated clays 

 of Gay Head on Marthas Vineyard, repre- 

 sents a prolonged period in the geological 

 history of the Coastal Plain equal to the 

 entire Lower Cretaceous of Europe, i. e., 

 from the Wealden to the Gault of England, 

 or from the lowest Neocomian to the highest 

 Albian (Vraconnian)* deposits of the Con- 

 tinent. 



With this fact in mind we are prepared 

 to consider the still more startling state- 

 ments contained in Dr. Newberry's Flora 

 of the Amboy Clays. And first it will be 

 necessary to determine precisely what Dr. 

 Newberry meant by the Amboy Clays. 

 This is made sufficiently clear by the follow- 

 ing description (pp. 21-22): 



" The Amboy Clays, to which our atten- 

 tion is now more particularly directed, out- 

 crop in a belt extending diagonally across 

 the State, forming the east bank of the 

 Delaware Eiver for a long distance above 

 and below Philadelphia, leaving the Dela- 

 ware at Trenton and stretching across the 

 State at its narrowest point to Raritan Bay, 

 and thence, passing over the southern 

 portion of Staten Island, where, as in the 

 State of NeV Jersey, they are largely 

 worked for economic purposes. They are 

 then interrupted by the Narrows and New 

 York harbor, as well as by the crystalline 

 rocks which occupy New York Island and 

 underlie the northern portion of Brooklyn 

 and the adjacent shores of Hell Gate. 

 Eastward of this the Amboy Clays are 

 generally covered with drift, but they ap- 

 pear at Glen Cove, Sea ClifiF, and various 

 other points on the north shore of Long 

 Island, where it has been deeply cut into by 

 glacial action and is now occupied by inlets 

 from Long Island Sound. Possibly the 

 whole length of Long Island is underlain by 

 the Amboy Clays, as characteristic fossils 

 *See 16th Ann. Rept. U. S. Geol. Sujv., p. 533. 



