102 



Its size, form, and nervation are, however, definite. It is at least 20 centi- 

 meters long, 19 centimeters broad in its widest part above the base, where it 

 is rounded downward to the petiole ; tapering upward, or narrowed in undu- 

 lating entire borders, to a slightly obtuse point; medial nerve half-round, 

 comparatively narrow; secondary veins mostly opposite, branching once, 

 rarely twice, all craspedodrome; basilar veins two pairs, the upper one in a 

 right angle to the medial nerve, forking ; the lower simple, thin, somewhat 

 deflected downward. This last character is marked by the end of one of the 

 basilar veins, distinctly seen near the border-base on the left side ; and it is 

 still more defined in the smaller leaf, (PI. xviii, Fig. 2,) which is subpeltate 

 by the border-base of the leaf covering the petiole. 



In the eight figures of leaves of Credneria which Stiehler (in Paleont, 

 he. cit.) has published, the basilar veins are thinner than in our large leaf, 

 but not more so than in the small one; and in all the European leaves referred 

 to Credneria, the second pair of lateral veins is at a greater distance from the 

 lower pair than from those above, even in the leaves with entire borders. They 

 have, therefore, a general appeai-ance more resembling that of species of Pla- 

 tanus. In the American leaves, this difference does not exist ; on the contrary, 

 the secondary veins are at about the same distance, except near the base, 

 where the lower pair, which may be considered as a marginal one, though 

 still of the same thickness, is nearer to the pair above. These secondary 

 veins are also more numerous. In this species there are nine to ten pairs 

 running straight to the borders, which they enter as craspedodrome, while the 

 European leaves have only four to six pairs, all the veins curving up in ascend- 

 ing to the borders, with mostly camptodrome divisions. These differences are 

 somewhat less marked, but evident, however, in the fine leaf which Heer has 

 described in the Cretaceous Moletin Flora as Credneria macrophylla, (PI. iv, 

 p. 16,) and which, besides, widely differs from ours by its very thick medial 

 nerve and its camptodrome secondary veins. It is of the same size and of 

 the same form, however. Heer rightly remarks, in describing this species, 

 "that the systematical relation of the genus Credneria is still very uncertain.'' 

 The same can be said of the species in relation to this genus, or of the rela- 

 tion of the leaves referred to it. 



Habitat. — South of Fort Harker, in a locality discovered by Chs. Stern- 

 berg ; both leaves. 



