308 MESOZOIC FLORAS OF UNITED STATES. 



on each side of the midrib are of equal length, are attached at light angles 

 to the midrib, and stand at right angles to it. They are so closely placed 

 as to touch one another, but sometimes, owing to pressure, which has 

 forced the margins of the leaflets into the rock substance, they are made 

 to appear narrower and hence farther apart. In shape the leaflets are 

 of equal width from base to tip, with a linear form. They are rounded 

 off at the free end so as to have a circular tip, or else are obliquely rounded 

 on the lower outer margin of the tip, so that this margin has an elliptical 

 outline. In all cases the extremity is very obtuse. At the end attached 

 to the midrib the leaflet is truncate, with corners rounded. The leaflet 

 appears to be placed on the upper surface of the midrib, with its base 

 not fusing with the midrib, and terminates with a raised line, so that 

 it appears superposed and adhering, showing the entire length distinct. 

 The basis of leaflets on opposite sides are so closel}^ placed that the}'' 

 almost touch. The}" are opposite or subopposite. The widest leaflets 

 have a width of 4 mm. and the narrowest of 2 mm. The longest have 

 a length of 12 mm. and the shortest of 6 mm. The leaf substance was 

 thick and leathery, hiding the nerves. The nerves are slender and almost 

 always invisible. The}^ are seen only in the wider leaflets, where the 

 leaf substance has been peeled off, leaving imprints of the nerves in the 

 fine shale. Where seen the}^ are 8 to 10 in numl^er, but may be fewer 

 in the narrower leaflets. They go ofT at right angles with the midrib 

 and maintain the same angle, being strictly parallel. 



Dunker" gives a description of a plant which he calls Pterophyllum 

 Lyellianum that is very near to our fossil. Heer, in his description of 

 Zamites arcticus ,^ says that this plant is so like Z. arcticus that it is 

 difficult to give any distinction. The leaflets of Bunker's plant are only 

 somewhat broader and farther apart. Dunker gives four to five very 

 slender nerves as possessed by it. Heer rightly regards this not as a 

 Pterophyllum but a Zamites of the type of Z. arcticus. Sir William 

 Dawson, in his account of Kootanie plants, ■" describes forms of this type 

 of C3''cad. One of these, pi. i, fig. 5, he identifies with Heer's Z.acutipemiis. 

 One he makes a new species, Z. montana, pi. i, figs. 6, 6a, and one he does 



« MoDogr. der.Norddeutsch. Wealdenbildung, p. 14, pi. vi, figs. 1, la, 2. 

 i Fl. Foss. Arct., Vol. I, p. 82. 



^' On the Mesozoic floras of the Rocky Mountain region of Canada (Trans. Ro3^ Soc. Canada, Sect. IV, \'ol. 

 Ill), p. 7. 



