FLORA OF OLDER POTOMAC FORMATION. 401 



Second. Are the floras of the Arundel and .Patuxent formations, with their 

 primitive dicotyledonous types, of necessity Cretaceous? There is apparently no 

 question regarding the Cretaceous age of the Raritan and Patapsco formations, 

 the uppermost beds of the Raritan even containing floras that have been regarded 

 by Professor Ward as middle Cretaceous. The paleobotanists who have studied 

 the floras of the earlier formations admit that there are many forms which show 

 Jurassic affinities. Professor Fontaine, in his study of these floras, states that there 

 was an "overwhelming percentage of Jurassic types," but unhestitatingly refers the 

 Potomac flora as a whole to the Cretaceous, correlating the deposits with the Creta- 

 ceous beds of England. This view is held by nearly all paleobotanists who regard 

 the presence of dicotjdedons, although of primitive types, as unquestioned evidence 

 of the Cretaceous age of the Arundel and Patuxent formations. Further investi- 

 gations of these floras may, to be sure, lead to other conclusions, but large collections 

 have already been made, and the paleobotanists who have studied them have 

 registered their decision regarding the Cretaceous age of the deposits in no uncertain 

 way. 



From our present knowledge of the floras and faunas, it is appai'ent that there 

 is considerable disparitj' between the evidence afforded bj' vertebrate paleontology 

 and by paleobotany. At least such is the case if equal consideration is given the 

 conclusions of each group of investigators. It seems essential, however, to suspend 

 final decision of these questions until more exhaustive investigation of the faunas 

 and floras has been made throughout the entire coastal region. The authors therefore 

 temporarily place the boundary line between the Jurassic and Cretaceous at the 

 base of the Patapsco formation, but with the feeling that much doubt exists regard- 

 ing it, and that the question is far from settled (pp. 212-214). 



The facts here stated would seem sufficient to negative the con- 

 clusion drawn. The authors do not say that by Jurassic they mean 

 beds of Wealden age, and we are to infer that they regard the Patuxent 

 and Arundel formations as older than the Wealden of England and the 

 Continent and as near the age* of the Coral Rag, the Purbeck, or the 

 Kimmeridge. That dinosaurs and other saurians are found in the 

 Raritan, and even in the Matawan, effectually disposes of the claim 

 formerly made that these types absolutely demonstrate the Jurassic 

 age of any bed yielding them, and distinctively Jurassic species of sau- 

 rians have not as yet been found in the Older Potomac beds. The 

 occurrence of plants of "Jurassic affinities" does not prove their Jurassic 

 age. It is but natural that the hixuriant Jurassic flora, such as that 

 of Oroville, Cal., and of the Buck Mountain district in Oregon, should 

 persist to some extent through the Lower Cretaceous. In l^oth the 

 flora and fauna the Lower Cretaceous forms, while having "Jurassic 



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