164 COKEELATION OF THE POTOMAC FOKMATIONS 



seems probable that this general horizon in the Eocky Mountain area 

 has been regarded as Morrison, where it contains vertebrate remains and 

 Kootanie where it contains plant remains, while to the eastward it may 

 be represented by marine Comanchean deposits. The recent discovery 

 of a Sauropod dinosaur in the Trinity of Oklahoma adds probability to 

 this supposition. While it is no part of the present purpose to discuss 

 at length the stratigraphic or faunal evidence of the age of the Morrison, 

 the presence of the Patuxent-Arundel flora in the Kootanie and the 

 similarities between the Arundel and Morrison faunas would seem to 

 lend strong probability to the view that the Morrison is Lower Cretaceous 

 and not Jurassic. This probability receives additional support from the 

 admitted Upper Jurassic age of the underlying Baptanodon beds, so 

 called. 



The Upper Knoxville Floea 



The flora of the Cretaceous portion of the Knoxville beds in the 

 Pacific coast region of North America is an extensive one, although the 

 specimens are for the most part fragmentary and poorly preserved. A 

 total of 35 species is recorded from this horizon in the present list (see 

 supra). About one-third of these are specifically identical with or 

 closely allied to Potomac species. No dicotyledons are certainly known, 

 and the species with an outside distribution are either forms with a 

 considerable vertical range or are confined to Wealden, Neocomian, or 

 Barremian horizons. Since there is no known unconformity between 

 these beds and the Upper Jurassic portion of the Knoxville it is quite 

 obvious that the former must represent all of the Neocomian and prob- 

 ably the Barremian as well. 



The Horsetown Flora 



This flora is directly descended from that of the Upper Knoxville, 

 which it resembles in having 12 out of a total of 28 species in common. 

 Five fragmentary species of dicotyledons have been described from this 

 horizon by Fontaine. They are "s^ery incomplete and ambiguous, but 



