322 THE POTOMAC OR YOUIS^GEK MESOZOIC ELOEA. 



radiating from a point considerably above the base, principal ones turned 

 upwards, lesser ones turned outwards, and the smallest turned downwards ; 

 primary nerves send off branches very obliquely, so that they appear 

 almost dichotomous ; the primary reticulation, formed by branches from 

 these sent off nearly at right angles, is composed of large, irregularly 

 shaped meshes, mostly four or five sided, made by the meeting of branches 

 nearly at a right angle ; the ultimate reticulation is similar but smaller. 



Locality : 72d mile-post, near Brooke ; very rare. 



This fine leaf is a good deal like the living Menispennum Canadense, 

 but wants the acute summit of that leaf The base of the fossil is not 

 shown with sufficient distinctness to make it perfectly clear whether the 

 leaf is peltate or not. It seems to be deeply auriculate, the auricles over- 

 lapping largely. It occurs in the same stratum with the fine specimens of 

 Taxodium, Brookense, Aralicephyllum, Aceriphylhtm, Sassafras, etc. 



Menispermites tenuinervis, sp. nov. 



Plate CLXXII, Fig. 8. 



Leaf small, orbicular in shape, subpeltate ; leaf substance very thick ; 

 nerves very obscure and slender, only three seen, radiating from a point 

 some distance above the base of the leaf 



Locality : Covington street, Baltimore ; very rare. 



This plant looks something like a Lemna. The leaf is much smaller 

 than that of M. Virginiensis. 



ARISTOLOCHI^PHYLLUM, gen. nov. 



I place in this genus certain fragments which apparently belonged to 

 a large, rather coarse leaf, which has a strong likeness in its nervation to 

 Aristolochia. The fragments are too imperfect to permit the shape of the 

 leaf to be made out, but it was apparently similar to that of some species 

 of this genus. 



Aristolochi^phyllum crassinerve, sp. nov. 



Plate CLX, Figs. 3-6. 



Shape of leaf not seen ; the leaves were apparently large and rather 

 coarse ; leaf-substance thick ; petiole and primary nerves very strong and 



