DESCRIPTIONS OF SPECIES. 131 



characters of nervation and margin leaving it a question which it is now 

 impossible to decide. 



Formation and locality : Tertiary (Eocene !). Tongue Eiver, Montana. 



Viburnum lanceolatum Newb. 

 PI. XXXIII, fig. 10. 



Arm. N. Y. Lye. Nat. Hist., Vol. IX (April, 1868), p. 54; Ills. Cret. and Ten. 

 PI. (1878), PI. XVI, fig. 10. 



"Leaves small, narrow, ovate or ovate-lanceolate, rounded or slightly 

 wedge-shaped at the base, pointed above, coarsely and sharply serrate- 

 dentate throughout; nervation strong; midrib straight; lateral nerves 

 about five pairs, diverging from the midrib at an angle varying from 

 15 to 20 degrees, all slightly and uniformly arched upward, the basilar 

 pair each throwing out at an acute angle about six simple branches, 

 which terminate in the teeth of the margin, the upper branches supporting 

 each one or two similar branches near the summits ; tertiary nervation 

 fine, and undistinguishable in the fossil state." 



Collected by Dr. F. V. Hayden. 



In the regularity and precision of the nervation these leaves resemble 

 those of Carpinus, but in most species of that genus the serration of the 

 margins is double, while here it is single, and, except in one or two Old 

 World forms, the nervation of the leaves of the living species of that genus 

 is considerably different, the basilar pair of lateral nerves being much 

 shorter and simple or less branched. 



The style of nervation observable in these fossils occurs in one or two 

 species of Rhamnus, but is there very exceptional, and the marginal 

 serration of Rhamnus is rarely, if ever, so coarse as in the plant before us. 



In Zizyphus we have a similar nervation, and not a dissimilar style in 

 Celtis, but in neither of these have we such marginal teeth. In Viburnum, 

 however, we have some examples of leaves exhibiting a closer resemblance 

 to the fossils than any I have cited above, as in Viburnum erosum Thurnbg., 

 from Korea, and V. odoratissimum of Japan. In both these plants we find 

 leaves with a great development of the basilar pair of nerves, and a coarse, 

 acute, and regular dentation of the margin. 



Formation and locality: Tertiary (Fort Union group). Fort Union, 

 Dakota. 



