DESCRIPTIONS OF SPECIES. 99 



deposition of the Middle Cretaceous strata, may be accepted with a certain 

 degree of mental reservation. It is true, however, that there is a most 

 marked correspondence, both in external form and nervation, between the 

 living- and the fossil plants, the differences being no greater than we might 

 expect to find betweeii species of the same genus. The nervation of the 

 fossils is stronger and more regular, and the whole aspect of the leaf rather 

 neater and more symmetrical. 



With the material already before us we may at least infer that there 

 was living in the American forests of the Cretaceous period a Lauraceous 

 tree, bearing trilobate leaves, having the general aspect and nervation of 

 those of our Sassafras. 



The large collections made from the Dakota group at Fort Harker and 

 elsewhere siuce the above note was written have included a great num- 

 ber of trilobate leaves, which are not separable by any constant and 

 well-marked character from those which formed the basis of the above 

 description, viz, figs. 1 to 4, PI. VI. On these, however, Lesquereux has 

 established a number of species of Sassafras, namely, S. acutilobum (the 

 form figured on PL VII, fig. 1), S. Harherianum (shown in our fig. 2, PI. 

 VIII), S. Mudgei, (PL VII, fig. 2) 8. obtusion (PL VIII, fig. 1), S. subin- 

 tegrifolius (PL VII, fig. 3), etc. 



A very large number of beautifully preserved specimens collected by 

 Mr. Sternberg at Fort Harker, and which have been submitted to me for 

 examination, show so many connecting links between these different forms 

 that I am quite unable to separate them into distinct species. 



Formation and locality: Cretaceous (Dakota group). Blackbird Hill, 

 Nebraska; Fort Harker and Smoky Hill Fork, Kansas. 



Sassafras cretaceum recurvatum (Lesq.) Newb. 



PI. IX, fig. 2. 



Sassafras recurvatus Lesq. Hayden's Ann. Rept., 1872 [1873] p. 424. 

 Platanus recurvata Lesq. Cret. Fl. (1874), p. 71, PI. X, figs. 3-5. 



Note.— Dr. Newberry considered this leaf to be a variety of his S. cretaceum, 

 as indicated by a memorandum on the margin of the plate. — A. H. 



Formation and locality: Cretaceous (Dakota group). Fort Harker, 

 Kansas 



