278 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



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

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

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

 to authorize a separation of species. 



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

 conte, Dr. F. V. Haijdcn). 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 lihamnea. The leaves of Ilhanmus are alternate, either 

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

 lanceolate, oblong, often glabrous, entire or witli 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, j^arallel, 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 Scliimper, to some Euphorbiacece,\\\\e Bridella, a New 

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

 the Morece. In this uncertainty, and without sufficient means of comparison 

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

 division. Moreover, I find in species of ii/««w«?/."t, especially oi' Ii/uimnidiuin 

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



Rliamniis alatcrnoides, Heer. 



Plate LII, Figs. 11,11a. 



lihamnua alulrriiohles, neer,Fl. Tert. Helv., iii, p. 7f*, pi. cxxiv,Cgs. 21,23.— Lesqx., Aunu.al Report, 1873, 

 p. 405. 

 Leaves small, subcoriaceous, elliptical, obtusely po'nteil, uarrowed to the jetiolo, dentate. 



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

 pair of lateral nerves opposite, 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 enlirc, the 



