26 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



rows appressed, those of the upper and lower ranks orbicular or obovate, 

 shortly mucronate, lateral ones longer, subulate, terminating' in awnlike 

 points; larger branches naked or bearing closely appressed linear scalelike 

 leaves." 



This is a very distinct and beautiful species collected by Dr. Hayden, 

 near Fort Union, Dakota, presenting marked differences from any known 

 living or fossil members of the genus. 



Its most remarkable character is its slender and graceful habit, and the 

 separation of the pairs of leafy branchlets along the naked and slender 

 branch. The leaves, too, are less crowded than in most other species, and 

 the lateral ranks are prolonged into acute awnlike points, all of which must 

 have given it an aspect considerably unlike that of any species hitherto 

 described. 



At the time this species was described no true Thuja had been recog- 

 nized in the fossil state. Thuites salicomoicles (Ung. Chlor. Prot. PI. II, fig. 

 1 ; XX, fig. 8) is regarded by Endlicher and Heer as a Libocedrus, to 

 which it certainly seems, judging from the figures and descriptions given 

 of it, to be more closely allied than to Thuja. Since that time, however, a 

 number of fossil plants have been referred to the genus Thuja, principally 

 derived from the amber. One species, T. saviana, Gaud., Neue Denkschr. 

 Schweitz. Gesell., Vol. XVII (1860) Fl. Foss. Ital., 3d Memoir, p. 12, PL 

 I, figs. 4-20; II, figs. 6, 7, has been established upon the fruits as well 

 as the foliage, so that there can be no question in regard to its botanical 

 position. Another species, T. mengeanus, Goepp. and Ber. Monogr. Foss. 

 Conif. (1850), p. 181, PI. XVIII, figs. 10, 11, resembles so closely our T. 

 occidentalis that it has been referred by Goeppert to that species. Besides 

 this, half a dozen additional species obtained from the amber have been 

 described by Goeppert from meager material and consequently somewhat 

 vaguely. It may be considered established, however, that during the 

 Tertiary age the genus Thuja was in existence and well represented in the 

 coniferous flora. The species now under consideration is represented by a 

 large number of specimens, though usually of small size, in the collections 

 made at Fort Union by Dr. Hayden, and has also been met with by Mr. 

 George M. Dawson in the Tertiary lignite strata of Canada. No fruit has 

 been found that can be certainly connected with the leaves, but there is in 

 the collection one imperfect cone derived from the same locality with the 



