278 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



and some of the authors quoted above, represent the divergence of tlie 

 secondary nerves quite in the same way as it is seen upon the specimens 

 of the Raton Mountains, and, therefore, no difference could be mentioned 

 to autiiorize a separation of species. 



Habitat. — Raton Mountains, near Trinidad, New Mexico {Dr. J. Le- 

 conte, Dr. F. V. Haydeti). By error, it was credited, in Annual Report, 

 1873, p. 105, to Marshall's Coal, Colorado, which is of the same group. 



RHAMNUS, Linn. 



The distribution of the species of this genus, both in the flora of our time 

 and in that of the geological periods, has been briefly indicated in the remarks 

 on the family of the Rhamncce. The leaves of Rhamnus are alternate, eitiier 

 coriaceous and persistent, or membranaceous and deciduous, ovate, obovate, 

 lanceolate, oblong, often glabrous, entire or with the borders more or less 

 minutely dentate. The nervation is pinnate, the lateral nerves mostly simple, 

 rarely branching, and camptodrome in the leaves, whose borders are entire, 

 close, parallel, connected with numerous distinct nervilles either in right 

 angle, or more generally oblique to the lateral nerves. Some of the species 

 described in this generic division are of a peculiar type, the secondary nerves 

 being very close, sometimes branching toward the borders. They may be 

 referable, according to Schimper, to some Euphorbiacea,\\\\e Bridelia^ a New 

 Holland genus, or, in the opinion of Saporta, to his genus Artocarpoides of 

 the MorecB. In this uncertainty, and without suflScient means of comparison 

 with living Australian plants, I have left them as formerly described in this 

 division. Moreover, I find in species of Rhamnus, especially oi Rltaninidium 

 of Brazil, characters in accordance with those of our leaves. 



Rhamnus alaternoidcs, Heer. 

 Plate LII, Figs. 11, 11 a. 



Jlhamnus alutenioicles, Heer, Fl. Tert. Helv., iii, p. 78, pi. cxxiv,figs. 21, 23.— Les(ix., Annual Report, 1873, 

 p. 405. 



Leaves small, subcoriaceous, elliptical, obtusely pointed, narrowed to the petiole, dentate. 



This small leaf, fourteen millimeters long, seven broad, has the lower 

 pair of lateral nerves opjiosite, and emerging a little above the base; the 

 others alternate, parallel, camptodrome, joined to the teeth by oblique veinlets, 

 and the borders distinctly dentate. It seems to agree in all its characters 

 with Heer's species, represented by three leaves, one of which is entire, the 



