110 



parallel, except the basilar one, which, following the curve of the borders, is 

 on a slightly more acute angle, numerous, fifteen to sixteen pairs, under a 

 general angle of divergence of 50° ; they slightly curve in ascending toward 

 the borders, where they bend, and which they follow, to anastomose with the 

 vein above; the nervilles are numerous, obsolete, parallel to the veins. By 

 its form, its short, slightly enlarged petiole, and its nervation, this leaf appears, 

 indeed, referable to Rhamnus, and has its analogies in a number of species of 

 the American Tertiary like Rhamnus salicifolius, Lesqx., R. cleburni, &c, 

 which all, however, have much thicker secondary veins. 

 Habitat. — Same locality as the former, Hayden. 



Terebinthinea. 



Juglans (?) debeyana, Heer, PI. xxiii, Figs. 1-5. 



Leaves coriaceous, entire, broadly ovate, obtuse, or with a short obtuse point, rounded-subcordate 

 at the base or narrowed downward by a curve, and slightly decurring to the petiole ; medial nerve thick ; 

 secondary veins numerous, open, camptodrome. 



PopulusQ) debeyana, Heer, Phyllites. p. 14, PI. i, Fig. 1. 



Juglans debeyana, Lesqx., American Journal of Science and Arls, loc. cit, p. 



101. 



From a single specimen submitted to his examination, Professor Heer 

 referred the leaf with doubt to Populus. A large number of good specimens 

 of leaves of the same species have been procured later, and some of the more 

 diverse forms figured in this memoir. These leaves vary from a broadly 

 ovate-obtuse to an elliptical form, the borders being always entire, rarely slightly 

 undulate, as in Fig. 1. The base is either slightly decurring to the petiole or 

 round-cordate; and though the borders are generally equilateral, they some- 

 times are more enlarged on one side, and the leaves, or rather leaflets, are curved 

 on one side, as in Figs. 4 and 5. This deviation, and also the difference in the 

 direction of the borders, as seen in comparing Figs. 1 and 3 to Fig. 2, indicates 

 a compound leaf : Fig. 2 representing a principal or top leaflet, the others rep- 

 resenting lateral ones. The nervation is rough and very distinct upon the im- 

 pressions of the lower side of the leaves, as in Figs. 2, 4, and 5. The secondary 

 veins are numerous, twelve to fourteen pairs, (in the leaf Fig. 2, which is 8 cen- 

 timeters long,) on an open angle of divergence averaging 60°, thick, variable in 

 distance, more or less parallel, separated by tertiary shorter veins forming, by 

 anastomose with the nervilles, a net of irregular, large, mostly quadrangular 



