L. F. WARD — PLANTS OF THE AMERICAN TRIAS. 25 



The flora of the Kootanie and the Trinity is very little known, but the Potomac 

 formation has furnished an abundance of vegetable remains; yet, no single species 

 of the Trias is found to occur in that formation. There are, however, six species in 

 the Potomac flora which resemble those of the Trias sufficiently to admit of com- 

 parison. ( )f these, three are ferns, two are cycads, and the remaining one is a Sagen- 

 opteris. As the local habitat of these species was nearly the same at the two 

 epochs, there is considerable probability that the Potomac plants may have been 

 the direct descendants of those of the Trias. 



Still, to all intents and purposes, the Triassic flora of the United States may be 

 regarded as a distinct and independent flora. So considering it, there are two 

 points of view from winch it can be treated when studying more especially the 

 question of its age : We may inquire first whether it constitutes one homogeneous 

 flora, or whether the different parts bear evidence of having been deposited at con- 

 siderably different periods of time. In the second place, we may inquire what its 

 relations are to other known floras of the globe — in other words, when treating of 

 the species of fossil plants found in this group, we naturally concern ourselves, first, 

 with their American distribution, and secondly, with their foreign distribution. 



American Distribution. 



I have divided the American plant-bearing Trias into five distinct geographical 

 areas, corresponding nearly with so many geological basins : 



First, that of the Connecticut valley, so long known to geologists from the dis- 

 covery in it of the tracks of animals. In this I assume the Southbury area, though 

 isolated geographically, to be included. 



Second, the New Jersey and Pennsylvania area, extending from the Hudson 

 river to the Potomac. I have not used the term "palisade area," which was em- 

 ployed by Professor Dana, because he makes this to include also the Triassic de- 

 posits of Virginia, and even to embrace the Richmond coal field. It would be 

 logical, it is true, to make this embrace the Piedmont deposits, extending as far 

 south as Charlottesville, in Virginia. Between this and the Virginia coal field 

 there is a complete interruption as greal as that between the Connecticut valley 

 and the palisades. As all these areas may have once been confluent, it is not con- 

 sidered important to maintain their strict geological relationships. 



Third, the Virginia area which I make to include all the deposits in that state, 

 those of the Richmond coal field having furnished nearly all the fossil plants. 



Fourth, the North Carolina basins or areas, including the North Carolina coal 

 field. The deposits in this state are not continuous, but consist of several isolated 

 basins. 



Fifth, the Western area. This includes all the deposits in Arizona and New 

 Mexico, and also in Colorado and other adjoining states and territories where 

 known, and constitutes the Shmanimp formation of Powell. Fossil plants other 

 than silicilied wood have been found only in New .Mexico in the vicinity of Abi- 

 quiu and the copper mines. Silicilied wood is found strewn ahout upon the plains 

 in vast profusion wherever t he formation exists. 



Keeping in view these live basins, it is necessary lirst to eliminate all the forms 

 which are confined to any one basin. We lind that out of a total of i pi species be- 

 longing to the American Trias, ;!:"> occur in the Connecticut valley, L8 in New 

 Jersey and Pennsylvania, 56 in Virginia (including the single species found in 



l \ Bull. Gi ol. Boo. Vm., Vm . :'., Ism 



