424 



ON SPECIES OF FOSSIL PLANTS 



" I doubt very much whether they can be considered as representing by themselves a defi- 

 nite stage, for they occur wherever the white clays are immediately overlaid by the highly 

 ferruginous strata of the Orange Sand." Prof. James Safford, who has studied the same 

 group in Tennessee, writes : " That the lithological differences do not indicate any distinct 

 formation ; and that the red shales are simply local beds or layers generally of very limited 

 extent." The question of synchronism is perhaps satisfactorily settled by these remarks. 

 Nevertheless, as the plants have not been found at the same locality, in strata of various 

 lithological compounds, they might, by their specific differences, indicate peculiar stages 

 of a same geological series. Prof. Hilgard appears to have this view. For, in his general 

 section of the Tertiary of Mississippi* under the general division of Lignitic of Northern 

 Mississippi, or Northern Lignitic group, underlying the Claiborne group, he places the 

 leaves-bearing strata in the following order : 



a. Gray clay and sands of Tippah, sometimes transformed into red shale. (Contains all our species of leaves 



marked red shale.) 



b. Gray clay of Lafayette and Calhoun, with Sabal, &e. (Contains the species marked white soft clay.) 



c. Gray clay of Winston, with Calamopsit. (Contains the species marked yellow coarse clay.) 



The leaves on brown sandstone, Ciunamomum, arc placed by the author with the 

 division b, a connection which docs not seem in accordance with what is shown by Ins 



diagram, page 116. 



In considering the plants by themselves, and studying their relation of forms, we find 

 in the red shale, twenty-two species described here from the Mississippi, and ten species 

 formerly clcscribed,t from Somerville, Tennessee ; in all thirty-two species. Prom the 

 white soft clay of both States we have six species only. None of these arc either identical 

 or even analogous with those of the red shale. Indeed, taken altogether, the flora of each 

 deposit has a peculiar facies. The first contains Oaks, Poplars, Magnolias, mostly forest 

 species, while the other has the Willows and the Palms, rather swamp plants. Between 

 the species of the white clay and those of the coarse yellow clay, though the number is 

 very limited, there is on the contrary as great an analogy as between the lithological com- 

 pounds of the strata. They have in common Ceanothus Meigsii, abundant in the white 

 clay of Tennessee as in the yellow clay of Mississippi. One has a Palm, Calamopsie, the 

 other has one also, a Sabal, both apparently belonging to those dwarf Palm trees which 

 generally inhabit deep swamps. In the yellow coarse clay we find a link of connection 

 with the flora of the red shales in Bsrsed 'lancifolia, which is common to both. 



Though the differences even in the general facies of these fossil plants may be well 



* Report on the Geology and Agriculture of the State of Mississippi, page 108. 

 f American Journal of Science, § 2, vol. xxvii, page 363. 



