64 THE OLDEE MESOZOIC FLOEA OF VIRGINIA. 



base, unequal in length, separate to the base, and exactly linear, not contracted at 

 base, rotundate-truncate at the extremities. Nerves parallel to the margin of the 

 pinnae and to one another and simple. 



The plants of this genus are few, both in species and individuals, in 

 the Mesozoic beds of Virginia. The number of individuals is especially 

 small, and this suggests the idea that the genus is in process of decadence. 

 This statement applies to the true Pterophyllum plants with the generic 

 character above given, and of the type of Pterophyllum longifolium, Brongt. 



Pterophyllum inaequale, spec. rtOT. 



Plate XXXVI, Fig. 1. 



Leaf elliptical in outline, midrib strong, with a raised line, or cord, in the middle, 

 tapering very gradually to the summit. Leaflets standing at right angles to the stem, 

 and united at their lowest portions next to the midrib by a slight expansion of their 

 bases. From the point of union to their summits they are of equal width, and at the 

 summit are rounded off into an elliptical or rotundate-truncate tip, which is always 

 bluntly ended. Leaflets of the middle portion of the leaf longest, attaining an extreme 

 length of 5 J centimeters, gradually shortening from the central portions towards the 

 base and summit of the leaf, and some distance from the summit suddenly diminishing 

 in length, and then from this point gradually again shortening. They vary in width, 

 narrow and wide leaflets occurring in an irregular manner. The widest are 7 milli- 

 meters, and the narrowest 3 millimeters wide. Nerves strong and distinctly defined, 

 forking immediately at their emergence from the midrib, and from that point simple, 

 parallel to one another and to the margin of the leaflets. Nerves of the middle and 

 lower leaflets go off from the midrib differently from those of the upper leaflets. In 

 the former the middle nerves of the leaflets go off at right angles to the midrib, and 

 maintain this direction to the end of the leaflets. Those near the upper and lower 

 margins of the leaflets go off somewhat obliquely, and arch away from the midrib to 

 assume a position parallel to the central nerves. Nerves of the upper leaflets all go 

 off obliquely, and curve strongly away from the midrib, assuming a position parallel 

 to one another in entering the leaflet. 



The upper and lower parts of this plant were not seen, as the most 

 complete specimen, the one figured, was lacking in these parts. Only this 

 specimen and a small fragment of another were found. The plant has 

 several features which are quite characteristic. The peculiar sudden abbre- 

 viation of the leaflets towards the summit of the leaf, and the intermingling 

 of leaflets of different widths in an irregular manner, are seen in no other 

 Petrophyllum known to me. The midrib seems to have been fleshy and 

 covered with a thick, dense epidermis. The elliptical outline of the leaf 



