160 Correlation" of the Potomac Formations 



species.^ A large number of the genera, however, are ■vvell-known Jurassic 

 types, and it is this feature which gives the apparent Jurassic f acies to the 

 Potomac, Wealden, and other ISTeocomian floras. 



Sixteen Patuxent species, some of which are doubtful determinations, 

 are present in the European Wealden floras, while 3 additional species 

 are recorded from floras which are classed as ISTeocomian. There are in 

 addition 12 species which are very similar to foreign Wealden and ISTeo- 

 comian types, as indicated in the table of distribution. There are 13 

 species present in the foreign Barremian, and 11 additional species 

 which are closely allied to Barremian types. 



Comparison with Aptian floras shows 2 identical species and 4 addi- 

 tional allied forms. Eight species continue in the European Albian and 

 11 additional are similar to European Albian species, largely those of 

 Portugal. When these facts are considered along with those furnished 

 by the Arundel reptilia, and when the Patuxent-Arundel floras are 

 studied in comparison with those from other American Lower Cretaceous 

 localities, the conclusion is reached that the Patuxent and Arundel for- 

 mations considered as a unit represent all except possibly the earliest 

 part of the Neocomian and all of the Barremian of the standard Euro- 

 pean section. 



Turning to the Patapsco flora it may be noted that none of the species 

 which are peculiar to this flora, when compared with the underlying 

 Patuxent-Arundel floras, occur in the European Cretaceous except Cissites 

 parvifolitis, which is found in the Albian of Portugal. A considerable 

 number, however, among which may be mentioned Cyperacites potoma- 

 censis, Populophyllum reniforme, CelastropJiyllum acutidens, and Sassa'- 

 fras potomacensis are represented by closely allied species in the Albian of 

 Portugal. Moreover, the latter flora closely parallels the Patapsco, in that 

 both mark the first abundant appearance of undoubted dico'tyledons and 

 a persistence of a considerable number of the earlier Cretaceous types, 



^Dioonites BucManus and some few other species have been recorded by 

 various students from Jurassic deposits but the identifications are not above 

 suspicion. 



