DESCRIPTIONS OF SPECIES. 129 



nearly equally toothed; nervation strong, medial nerve straight, bearing 

 eight or nine pairs of lateral nerves, which diverge at an angle of about 

 45 degrees. The basilar pair of lateral nerves each sending off five or six 

 branches on the lower side, which are again branched and terminate in the 

 teeth of the margin. The second pair of lateral nerves have each four 

 similar branches, the third pair three, the fourth pah- two, the fifth pair one, 

 though there are frequent departures from this rule. The tertiary nerves 

 are strongly marked, leaving the secondary nerves nearly at right angles, 

 crossing directly between the adjacent ones, or anastomosing with some 

 irregularity in the middle of the interspaces." 



Collected by Dr. F. V. Hayden. 



There are many fragments of these leaves in the collection before me, 

 embedded in a very fine and hard argillaceous limestone, and very beauti- 

 fully preserved. They exhibit considerable resemblance to the leaves of 

 Morus, especially M. rubra, but in that plant the basilar nerves of the leaves 

 are more developed and reach the margins higher up. The marginal den- 

 tation is also generally more acute in the leaves of the mulberry and the 

 leaves more pointed. The nervation of these fossil leaves is almost pre- 

 cisely that of our common species of Tilia, but in that the marginal denta- 

 tion is much sharper. In a Southern species, however, T. heterophylla, I 

 have found leaves which seem to be the exact counterpart of these; leaves 

 with a roughish surface, strong and regular nervation, just after this pat- 

 tern, and with a coarse, obtuse, and regular dentation. I am, therefore, 

 inclined to refer these fossils to Tilia, and to regard them as the relics of a 

 species closely allied to, if not identical with, T. heterophylla. 



Formation and locality: Tertiary (Eocene?). Near Fort Clarke, Dakota. 

 Viburnum asperum Newb. 

 Pi. XXXIII, fig. 9. 



Ann. N. T. Lye. Nat. Hist., Vol. IX (April, 1868), p. 54; Ills. Cret. and Tert.Pl. 



(1878), PL XVI, fig. 8. 



"Leaves ovate in outline, rounded or slightly cordate at base, acute 

 and long-pointed above, margins all cut by relatively large acute teeth; 

 nervation strong, crowded; midrib straight; lateral nerves alternate, about 

 nine on each side, the lowest and strongest bearing each five to six simple 

 branches on the lower side; the lateral nerves of the middle of the leaf 

 mon xxxv 9 



