THE CRETACEOUS RIM OF THE BLACK HILLS. 201 



large number are composed of only one or two cells. The annual 

 rings are rather indistinct, yet can be made out. 



" As far as I now know, only two species of Araucarioxylon have 

 been described from the United States, A. Arizonicum Kn., from the 

 Triassic or Lower Jurassic of New Mexico and Arizona, and A. 

 Virginianum Kn., supposed at first to belong to the Potomac 

 formation, but now known to be from the Trias of Virginia. 

 These species differ markedly from the one under discussion. 

 With the A. Arizonicum it has almost no points in common, while 

 it differs from the A. Virginianum in important particulars." 



The only sections of the fossil wood that have yet been made 

 were cut from a specimen taken from the cycad bed proper and 

 not from the principal fossil forest, but it often happens that 

 only one species can be found in such a forest. It is therefore 

 probable that the same structure would be shown by. the other 

 specimens. I confess to a little surprise at finding that this 

 structure represents the Araucarian rather than the Sequoian 

 type of conifers, since, in the east at least, these two types char- 

 acterize the Trias and Potomac respectively, no Araucarian speci- 

 mens having been found in the Potomac and no Sequoian speci- 

 mens in the Trias. And generally the Araucarian type is more 

 ancient. This evidence therefore points to a lower instead of a 

 higher horizon. 



I have made a somewhat careful study of the specimens from 

 the plant bed above Evans Quarry, and have asked Professor 

 Knowlton to assist me, his experience in recently editing Les- 

 quereux's Flora of the Dakota Group having familiarized him 

 with the forms of that age. The result of our joint investigation 

 may be summed up as follows : 



The specimens are few and fragmentary, and the only species 

 that can be even approximately determined are : 



Asplenium Dicksonianum Heer. 



Quercus Wardiana Lx. ? 



Lindera venusta Lx. 



Aralia Towneri Lx. ? 



Virbunites Evansanus n. sp. 



