60 Later Extinct Floras of North America^ 



which, if fossilized, would form impressions absolutely (indis- 

 tinguishable from tlinii. ami I have therefore found it impossi- 

 ble to fix upon any characters by which they can be separated. 

 As compared with the fossils which 1 have referred to C. ros- 

 tratOj these leaves arc a little more rounded in outline, the 

 nervation somewhat more open and delicate, the marginal teeth 

 more nearly equal in size, and more obtuse. 



Of all the Bpecies of Corylus, living or fossil, which have been 

 described, there is none of which the leaves so much resemble 

 these, as C. Americana. 



Formation <ut<} Locality. Miocene Tertiary strata. Fort 

 Union, Dacotah. (Dr. Hay den.) 



Cor. i in* rostrata. (Ait.) 



These leaves offer no characters by which they can be dis- 

 tinguished from those of the living " Beaked Hazel-nut." They 

 are clearly those of a Hazel, and show such a perfect correspon- 

 dence with those of one of the species living in the region where 

 these fossils occur, that until the fruit shall be found, and the 

 question definitely settled, I have thought it best to consider 

 them as identical. 



Formation and Locality. Miocene strata. Fort Union. 

 (Dr. Harden.) 



Po|hiIii* cordata (n. sp.) 



Leaves orbicular or round-heart-shaped, deeply cordate at the 

 base; margins strongly toothed, exoept the inner border of the 

 lobes of the base ; nervation radiate; medial nerve straight, simple 

 below, branched mar the summit ; lateral nerves, 8 pairs diverging 

 at nearly equal angles, from a common point of origin; lower 



lateral nerves small, simple, arched upward at their summits, ter- 



minating in the margins; second pair of lateral nerves springing 

 from the basal poinl of radiation nearly at right angles with the 

 midrib, arching upward as the} approach the lateral margins, and 

 supporting each about three branches on the inner side; third pair 



Of lateral nerves diverging from the midrib at its base at an angle 



of about i''-, bearing one or two lateral branches, and terminating 

 in the margin above the middle of the leaf 



