106 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



and described some of them in his Cretaceous Flora under the name of 

 Sassafras (Araliopsis) mirabile. 



Count Saporta has raised the question whether any of the trilobate 

 leaves referred by Lesquereux and myself to Sassafras really belong to 

 this genus, and has suggested that their affinities are more likely to be with 

 Aralia. This question can only be definitely settled by the discovery of the 

 fruits of the tree which bore these leaves; these will undoubtedly be found 

 when they are carefully looked for by collectors. Waiting such time, 

 however, we may say that some of the many trilobate leaves found in the 

 Dakota group by their form and nervation are much more like the leaves of 

 Sasafras than those of any other living genus. In these the form is ele- 

 gantly trilobate, the margins entire, the lobes rounded or obtusely pointed; 

 the nervation is camptodrome. Possibly these leaves will be found to shade 

 into those now under consideration, but judging from the material now 

 before us the difference is considerable. For example, these leaves are 

 larger, have a waved and sometimes even denticulate margin above, while 

 the nerves are stronger and straighter, terminating in the denticles of the 

 border. In all these respects they are more like the leaves of Platanus 

 than those of Sassafras, and they are therefore for the present retained in 

 the genus to which they were referred in the first published description. 



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

 Nebraska. 



Platanus nobilis Newb. 



PI. XXXIV; XXXVII, fig. 1; L, fig. 1. 



Ann. N. Y. Lye. Nat. Hist., Vol. IX (April, 1868), p. 67; Ills. Cret. and Tert. PI. 

 (1878), PI. XVII; XX, fig. 1, under P. Haydenii. 



" Leaves large, 1£ feet in length and breadth, petioled, three-lobed or 

 subfive-lobed, lobes acute, margins of lobes and base entire, or near the 

 summits of the lobes delicately sinuate-toothed; nervation strongly 

 marked, generally parallel; medial nerve straight, two basilar nerves of 

 nearly equal length and strength diverge from it at an angle of 30 to 35 

 degrees, are straight throughout, and terminate in the apices of the 

 principal lateral lobes. Above the basilar nerves about 16 pairs of lateral 

 nerves are given off from the midrib at about the same angle; these are 

 nearly straight and parallel, terminating in the teeth of the margin. From 



