28 PROCEEDINGS OF WASHINGTON MEETING. 



of New Jersey and Pennsylvania, has 72 per cent of its plants common to other 

 basins, while that of North Carolina has 52 per cent common. These two remark- 

 ably exceptional cases are the smallest of the five basins. Of the three principal 

 basins, that of the Connecticut valley has 39 per cent ; that of Virginia, 39 per 

 cent ; and that of North Carolina, 52 per cent of common species. 



Considering that we are dealing with a fossil flora, a large number of whose 

 forms are not specifically determinable and most of the material of which is frag- 

 mentary, the fact that in all but one of these five florules of the American Trias 

 the number of forms sufficiently distinct to be clearly determinable specifically 

 and to be identified with forms in other basins, ranges from 39 to 72 per cent may 

 be taken as very strong evidence of the general parallelism of these four basins. 



As regards the western deposits, notwithstanding the poverty of their present 

 known flora, there seems to be some indication that they were not laid down at 

 the same exact epoch as those of the Atlantic coast; but, assuming such an asyn- 

 chronism, the question as to whether they are earlier or later cannot be profitably 

 considered with the present insufficient data. 



Foreign Distribution. 



The foreign distribution of the Triassic flora has been a much more difficult 

 problem, and has required a large amount of careful analysis. Five tables have 

 been prepared with the object of exhibiting it to the fullest possible extent.* In 

 discussing this problem all species which are entirely without foreign distribution 

 or affinity are of course omitted. The remainder are divided into two classes: 

 First, those which are actually found in other formations and localities than the 

 American Trias; and second, those which, though not so found, are obviously re- 

 lated to other species that are. There are 40 species belonging to the first, and 

 17 to the second of these two classes, making 57 species which have diagnostic 

 value in determining the age of the formation. 



In the first or most extended of the tables of foreign distribution, these 57 species 

 are introduced and the foreign distribution, both geological and geographical, is 

 shown. The amount of detail, however, is so great that it is impossible to discuss 

 the problem without further analysis. The first step in such analysis has been the 

 preparation of a table from the geological point of view, giving under each forma- 

 tion the species which are common to it and the American Tiias. In some respects 

 this table goes still further into details than the former one, and a full explanation 

 of many of the cases presented in it is made. 



The third of the tables of foreign distribution relates exclusively to the first class 

 above named — that is, to the American Triassic species which have a foreign dis- 

 tribution, — and gives each species with such distribution, only, however, as regards 

 the ge< (logical position, leaving the geographical range to lie determined by reference 

 to the table last considered. 



finally we have a recapitulation of all the data thus far set forth showing the 

 number of species occurring at each of the other horizons in the total distribution : 



♦Several large charts illustrating so far as possible the- data contained in these tallies were ex- 

 hibited before the Society. These cannot conveniently be introduced here, but will appear in the 

 final essay. 



