144 UiilTED STATES GEOLOGICAL SUKVEY— TERTIARY ELOEA. 



CORYLUS, Toum. 



This genus at our time is represented in the northern hemisphere only. 

 Of the seven species by which it is now known, two inhabit eastern Asia; 

 three are found in Europe, none being confined to that continent, however, for 

 two extend to Asia and one to Algeria. Two belong exclusively to North Am- 

 erica: Corylus Americana, wiiose range of distribution is from Florida to 

 Saskatshawan, and C. rostrata, which does not go southward far beyond the 

 Alleghany Mountains, and ascends only to the great lakes. In the fossil flora, 

 three species only. are known by their leaves in the Miocene of Europe. 

 One of them is nearly exclusively Arctic, its remains being found in great 

 abundance in the Miocene of Greenland. It is, however, quite as common 

 in the same formation of Alaska, and appears more rarely in the Miocene of 

 the Rocky Mountains. The specimens figured as marked below are from 

 Carbon and the Washakie group; some fragments, in a bad state of preserva- 

 tion, and therefore somewhat uncertain, have been found at Evanston. Four 

 species of Corylus are described from the Union group by Dr. Newberry. 

 From the similarity of the leaves of C. Mac Quarrii with those of our present 

 species, it appears certain that these had their origin in geological times as 

 far up as the Miocene at least, and also that their present characters and their 

 distribution agree with those of their ancestors. 



Corylus mac Quarrii, (Forbes) Heer. 



Plate XVm, Figs. 9-11. 



AlnitesT Mac Qitarrii, Forbes, Qn.irt. Journ. Geol. Soc, 1851, p. 103. 



Cwylui Mac Quarrii, Heer, Fl. Arct., p. 104, pi. viii, figs. 9-12, ix, figs. 1-8, xvii, fig. bd, lix, fig. 7o, p. 



138, pi. xxi, fig. 11 c, xxii, figs. 1-6, xxiii, fig. 1, p. 149, pi. xxvi, figs. 1 a, 2-4, xxi, fig. 5 ; Fl. 

 ' Foss. Alask., p. 29, pi. iii, fig. 9, pi. iv; Foss. Fl. of N. Greenl., p. 469, pi. xliv, fig. 11a, 



xlv, fig. 66; Spitzb. Fl.,p. 56, pi. xi.figs. 10-13, xiii, fig. 35 6.— Lesqx., Annual Report, 1871, 



p. 292 ; Supplemeut, p. 9. 

 AInu» pseudoglutinosa, Goepp., Tert. Fl. d. Polar Gcg., 1861. 

 Corylus grosae-serrala, Heer, Fl. Tert. Helv., ii, p. 44, pi. Ixxiii, figs. 18, 19. 



Leaves of medium size, very variable, oblong or oval, pointed or acuminate, ronnded, truncate or 

 omargiiiate at the base, triply serrate, penninerved ; lateral veins thick, branching, craspedodromo, like 

 their divisions. 



The immense number of specimens, some of them in a p.3rfect state of 

 preservation, which have been examined by Prof Heer, have enabled him to 

 compare the various forms of these leaves, and to refer them to the same spe- 

 cies. Seen separately in two or three fragmentary specimens, Hke those fig- 

 ured here, it is difficult to find their points of identity, and therefore easy to 

 refer each leaf to a diiferent species. The surface of these Corylus leaves is 



