68 Later Extinct Floras of North America, 



side, and 4-5 on the upper si.le near the summit, all of which termi- 

 nate in the margins. The tertiary nerves connect the adjacent 

 secondary nerves nearly at right angles : sometimes they are straight 

 and parallel, but oftener more or less broken and branching where 

 they meet, near the middle of the interspaces. Where the systems 

 of nervation of the lateral and middle lobes come in contact, the 

 tertiary nerves are Stronger, ami form a somewhat irregular net- 

 work, of which the areolae are large and sub-quadrate. 



In general aspect these magnificent leaves are considerably 



unlike those of any known species of Platanus, and I have 

 felt considerable hesitation in referring them to that genus. 

 The texture was evidently thicker and the surfaces smoother 

 than in the leaves of most Sycamores, and, on the whole, 

 they recall the leaves of Cecrqpia, or some other of the broad, 

 leathery, polished leaves, borne by the trees of the tropics. 

 On close examination, however, they are found to present the 

 radical structure of the leaves of Platanus, and, aside from 

 their association with so many genera plainly belonging to the 

 flora of the temperate zone, their form ami nervation seem to 

 me t" afford at least presumptive evidence that they were borne 

 by a tree of that genus. They will, perhaps, Buggesl to the 

 1 botanist the leaves described by Unger under the 

 names of Platanus Hercules, P. Jatrophcefolia, etc. (Chlorie 

 Protogsea, p. L37, T. xlv., figs. f',-7, etc.). and which he subse- 

 quently removed from that genus; but those palmate, many- 

 lobed leaves were very unlike these now before us, and resem- 

 ble much more the leaves of Jatropha or StercuUa, than those 

 of Platanus. 



The crowded, somewhat heavy, ami regular nervation of these 

 leaves, their thick texture and polished surface, must have 

 given the tree «.n which the} grow an aspecl quite different 

 from that of /'. occidentalism but /'. orientalis, and sometimes 

 /'. raa mesa, have thick and polished Leaves, and the deviation 

 from the common form is not so great in these fossils as in the 

 living species I have named, or the fossil species named 1>\ 

 [Jnger /'. grandifolia and /'. Sirii (Ohlor. Protogeea and 

 9, l'l"i\ v., Botzka i. 



