158 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



borders. The nervation is as irregular as tlie form, being tripalmate at the 

 base, with the lateral veins, one only and branching on one side, wbile on the 

 other they are double and parallel, with three pairs of secondary veins above, 

 at a distance from the primary nerves; a nervation related to that of Plata- 

 nus. Indeed, by its sharp teeth, turned upward, this peculiar leaf might be 

 taken for a deformity of the common P. aceroides or P. Guillelma, but for 

 its remarkable shape. As it comes from the same locality as the specimens 

 of the following and apparently very variable species, it may belong to it. This 

 possible relation indicates its place in this genus. It seems to represent a 

 transitional form between the dentate and the lobate leaves of Quercus. 



Habitat. — Laramie Plains, near Rock Creek, Wyoming {Dr. F. V. 

 Hayden). 



Quercus acrodon, Lesqs. 

 Plate XIX, Figs. 11-13. 

 Quereas acrodon, Lesqx., Annual Report, 1869, p. 196 ; 1872, p. 389. 



Leaves oval or obovate, more or less rapidly narrowed upward to an acute point and downward to 

 the petiole; borders sharply deeply dentate; lateral nerves parallel, equidistant, craspedodrome. 



The three fragments figured here expose the general characters of the 

 leaves of this fine species. The form is ovate, either narrowed in about the 

 same degree to an acute point and to the petiole (broken), as in fig. 12, or 

 obovate, rounded upward to a short point, and narrowed cuneiform to the 

 base. The borders are sharply dentate, sometimes with unequal teeth, as iu 

 fig. 13, but the teeth are all turning upward and deep, separated by obtuse 

 sinuses. The secondary nerves, mostly simple, some of them, however, 

 branching near the borders, pass up, all in the same angle of divergence, 40°, 

 either straight or slightly curving, entering the teeth as well as their branches. 

 The substance of these leaves is not coriaceous, the areolation being, how- 

 ever, rendered obsolete by a thin coating of carbonaceous matter. In fig. 11, 

 only the netting is distinctly seen, formed by veinlets in right angle to the 

 nerves, close, dividing, either obliquely or in right angle, into quadrangular 

 meshes. The base of the leaves only has entire borders. 



Like the former leaf, these have no direct relation to those of any fossil 

 species of Quercus published by authors. Among living species, its affinity 

 is with Q. agrifolia, Nee., of California. 



Habitat. — Same locality as the former {Dr. F. V. Hayden). 



