FLOIJA OF OLDER POTOMAC FOH.MATIOX. 401 



Second. Alt' tlic lioms of tlic Arundel niid Patiixciit lurinatidiis, witli tlieir 

 priniitiv.' dicol ylcdoiu.us types, of necessity Cretaceous^ Tliere is aiiparently no 

 question re,u;ardin^' the Cictaceous age erf the Ivaritan an<i Patapsco formations, 

 the ui)pennos! heds of the Ivaritan even coiitaininij; Ih.ras tliat have heen rejijinled 

 hv Pi-ofes.sor Wai-d as middle Cretaceous, 'llie paleohotanists who luive studied 

 the Horas of the earlier h.rmations admit that- there are many forms which show 

 Jurassic allinities. j'rofcssor Fontaine, in his study of these floras, states tliat there 

 was an •' overwhelmint;- percciitaf^e of Jurassic types," hut- unhestitatingly refers tlie 

 Potomac llora as a whole to the Cretaceous, correlating th.' deposits with the Crela- 

 eeou.s betis of Kngland. Thi> view is held hy nearly all paleohotanists who regard 

 the presence of dicotyledons, although of primitive types, as uncpiestioned evidence 

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

 gations of the.sc lloras may. to l>e sure, lead to otlier conclusions, hut large collections 

 iiave already been made, and the paleohotanists 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 apparent that there 

 is considerable disjiarity 1)etween the evidence afforded by 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. 21-2--214). 



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

 chision drawn. The authors do not say that l^y 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 

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

 formerly made that these types al)solutely demonstrate the Jurassic 

 age of any l^ed yielding them, and distinctively Jurassic species of sau- 

 rians have not tis yet been foutid in the Older Potomac beds. The 

 occiu-rence of plants of "Jurassic affinities" does not prove their Jurassic 

 age. It is l)ut 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 both the 

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



MON XI. VIII — ().5 26 



