880 SYSTEMATIC PALEONTOLOGY 



Description. " Leaves petiolate, decurrent at base, very smooth above, 

 strongly nerved below ; three-lobed ; lobes entire and acute. The nervation 

 is all strongly defined ; the central nerve straight or nearly so ; the lateral 

 primary nerve springing from it at an angle of 30 ; secondary nerves 

 regularly arched till they approach the margin of the lobes, when they are 

 abruptly curved and run together. From these the tertiary nerves are 

 given off at a right angle, and from these the quaternary nerves spring 

 at a similar angle, together forming a network of which the areoles are 

 subquadrate." Newberry, 1868. 



Professor Newberry includes under Sassafras cretaceum the various 

 forms described by Professor Lesquereux as 8. mudgei, S. subintegri- 

 folium, S. integrifolium, S. obiusum, S. cretaceum dentatum, 3. cre- 

 taceum obiusum, S. acutilobum, Cissites harkianus, and C. salisburice- 

 folius. While this shows the undoubted composite nature of S. cretaceum, 

 it also shows that the extremes of leaf form above mentioned are so closely 

 connected with the more typical leaf by a series of intermediate forms that 

 the question of where one species shall end and another begin is an 

 extremely difficult one. 



The writer considers the leaf figured by Prof. Newberry on pi. vi, fig. 1, 

 Later Ext. FL, to be the typical form of this species, thus agreeing with 

 Newberry's original description and with his later opinion expressed in 

 1898. This type bears considerable resemblance to some modern Sassa- 

 fras leaves. A slight widening of the terminal lobe of some of these in the 

 basal region would give a leaf strikingly like Araliopsoides cretacea ; or 

 were the sinuses of the latter slightly deeper we would have the typical 

 modern leaf. The basal portion of the leaf is like Sassafras, and the indi- 

 cations point to a similar venation in this region. The first pair of secon- 

 daries do not branch to form margins of the sinuses; the left one runs 

 directly to the sinus, however, and may possibly have conformed to the 

 margin and been effaced in the specimen ; the right one is stronger and 

 runs almost to the sinus where it makes a sharp turn upward, continuing 

 until it joins the next secondary. This feature is analogous to those in 

 the modern leaf, which may indicate the mode of origin of this peculiar 

 character. This leaf seems to form a central figure from which a series of 



