498 MESOZOIC FLORAS OF UNITED STATES. 



as P. schista, l)ut is rather larger. The wing, however, is elhptical in 

 foi'iii, and not divided as in that plant. It may be P. schista, as the amount 

 of material is not snfficient to determine its true character. 



POPULOPIIYLLUM ^fENISPEK^rOII)ES Wlinl 11. Sp. 



PI. ex. Figs. 2-4. 



Professor Ward has indicated, on labels accompanying it, a plant of the 

 Mount Vernon flora as a new species, with the name given al)ove. As no 

 description accompanies it, the description may be given here. The plant 

 is quite common on the Mount Vernon horizon, and a number of speci- 

 mens were obtained. They are chiefly fragments of leaves, mostly small 

 and imperfect. The specimen shown in PL CX, Fig. 2, from the White 

 House Bluff locality, may be taken as the type. It shows the dentation 

 better than the others. The specimens depicted in Figs. 3 and 4 are the 

 best obtained. Fig. 3, from the Mount Vernon locality, gives fragments 

 of leaves, showing the central parts from base to smnmit, but with the 

 right and left margins missing. By taking the missing parts from other 

 specimens a pretty good idea of the complete leaf may l^e formed. The 

 length indicated is 4 cm., and the width was probably greater. Its shape 

 seems to have been subreniform, ):)eing wider than long. The margin was 

 entire, or at most had shallow crenate teeth. The principal nerves radiate 

 from a common point at the base of the leaf and the summit of the petiole. 

 The middle nerve is stronger than those on either side. These principal 

 nerves split up, after the fashion of those of Menispermites, into secondary 

 ones. These curve to join adjacent ones of the same order, forming 

 large, more or less rounded, meshes. The secondary nerves send off 

 tertiaiy ones at nearly right angles, and these unite to form roimded 

 meshes. The minor nervation is a good deal like that of Menispermites. 

 The most important difference in the nervation from Menispermites is the 

 fact that the primary nerves radiate from the summit of the petiole at the 

 base of the leaf and not within the lamina. The plant shown in Fig. 3 

 gives the nerves distinctly. Fig. 4, also from the Mount Vernon locality, 

 shows a nearly complete leaf smaller than the average. 



This species seems to be specially characteristic of the White House 

 Bluff locality, the same number (12) of specimens occurring from there as 

 in the Mount Vernon collection, notwithstanding the much greater size 

 of the latter. The first and only specimen brought from the former 



