100 



of the discordance of their characters. A similar kind of variability is 

 remarked only, I think, in species of Quercus. Some leaves of oaks have the 

 double nervation camptodrome and craspedodrome upon the same leaf; some 

 others show a disposition to an unequal expansion of the limb on one side or 

 on the other, in relation to the unequal division of the veins ; even a nerva- 

 tion somewhat analogous to that of these leaves is remarked in some fossil 

 species, as in Quercus deslo'esi, Heer, Q. charpentieri, H, Q. agnostifolia, H., 

 &c. But this relation is too far ; the type is evidently original, aud for this 

 reason it had to be separated as of uncertain affinity. 



Habitat. — Near Beatrice, Gage County, Nebraska, Hayden. 



Protophyllum, Lesqx. 



Leaves generally of large size, thick, coriaceous, broadly oval or round-pointed, subpeltate; borders 

 entire or undulate ; nervation palrnato-pinnate ; lower primary lateral veins at a distance from the 

 border-base, with more or less numerous veinlets underneath, either in right angle to the middle nerve 

 or diverging downward ; upper lateral veins at equal distance from the lower pair and parallel, all 

 craspedodrome. 



In my examination of the numerous leaves described in this division, and 

 which I have previously referred either to Credneria or to Pterospermites, 

 I have never been able to recognize characters which might satisfactorily 

 account for this reference. If some of the leaves, like that of PI. xvi, of PI. 

 xvii, Fig. 1, or of PL xviii, Fig. 2, are referable to Credneria on account 

 of their size, their form, aud the lower horizontal veins at the base of the 

 leaves under the primary divisions, they do not show the characters indicated 

 by Zenker in the diagnosis of this genus in Paleont., V. II, p. 63, viz : Caulis 

 pohjgonearum, folia obovata, basi subcordata, longc-petiolata, nervi primarii sub- 

 erecti, etc. In regard to the nervation, all the Credneria leaves figured in the 

 same work with entire borders have a camptodrome nervation ; those witli 

 craspedodrome secondary nerves are dentate or lobed. In the beautiful 

 leaf described by Heer in Molet. Fl., (p. 16, PI. iv,) as Credneria macrophylla, 

 which, judging from our fragmentary specimen of Credneria leconteana, (PI. 

 xvii, Fig. 4,) is related by its form to the American species, the camptodrome 

 nervation is positively marked. 



Now, besides this difference between the European Crednerice and all 

 the Cretaceous leaves, with borders entire, which I have referred, until now, 

 to this genus, these still differ from the characters of Credneria by the over- 

 lapping of the border-base upon the petiole. These leaves are generally 



