/. W. Dawwn^Erian Flora of the United States. 343 



rows of slit-formed bordered pores in hexagonal borders. The 

 medullary sheath consists of psendo-scalariform and reticulated 

 fibers; but the most remarkable feature of this wood is the 

 structure of the medullary rays, which are very frequent, but 

 short and simple, sometimes having as few as four cells super- 

 imposed. This is a character not before observed in Coniferous 

 trees of so great age, and allies this Middle Brian form with 



ch have been supposed to belong 

 to Cordaites or Sigillaria. In any case this structure is new, 

 and I have named the species Dadoxylon Clarkii, after its dis- 

 coverer. Tin- specimens occur. ;u n nu to Professor Clarke, 



>us layer which is tilled with the minute shells of 



ived to beaPteropod; and con- 



, and Gyroceras. The stems 



found are only a few inches in diameter, but may be branches 



of larger t 



that we already know five species of Conifer- 

 genera in the Middle Erian of America, 

 an interesting confirmation of the facts otherwise known as 

 Jo the great richness and variety of this ancient flora. Pro- 

 ( '"" Gueppert informs me that he has recently recognized 

 jmilar wood in the Devonian of Germany, and there can be no 

 * bat the fossil wood discovered by Hugh Miller in the 

 n Mi*"d Sandstone of .Scotland, and described by Salter and 

 M'N'ah. is of similar character, and probably belongs to the 

 genus Dadoxylon. Thus this type of Coniferous trees seems to 

 li:iv " I'rni as well c-:: ia led into species in 



the Middle Devonian as in the succeeding Carboniferous. 



III. The Genus Cladoxttlon in America. 



. In the Report of the Fossils of the Devonian rocks of Thu- 



I !,i.,r aral Kk-hter* the former has described and 



%ured cen acture, to which he 



h thus appe; 





