73 



denticulate, placed a little below the middle of the leaf, with three primary 

 nerves from a little above the base, and 7 to 8 pairs of secondary veins, par- 

 allel, close, at an angle of divergence scarcely more than 30°, straight to the 

 borders where they enter the teeth with their divisions. The other leaf (PI. 

 ix, Fig. 3) is much smaller, not lobate, and has the same kind of nervation, 

 except that the primary lateral veins are slightly alternate, not quite as thick 

 as the secondary veins above. This, like the other leaf, has its border den- 

 ticulate, with that peculiar kind of short outward-turned teeth, separated by 

 equal obtuse sinuses, remarked in Greviopsis haydenii ; Protophyllum mudgii, 

 &c. The nervation of these leaves, and also the decurrent prolongation of 

 their base below the division of the primary nerves, refer them to Platanus. 

 The leaves of young branches of P. occidentalis are often also without lateral 

 lobes, or have scarcely distinct lobes, and in that case their nervation appears 

 rather pinnate than palmate. 



Habitat. — Beatrice, Gage County, Hayden. Blackbird Hills, Marcou, 

 Capellini. I found it, too, near Decatur, Nebraska. 



Platanus diminutiva, Lesqx., PI. viii, Fig. 5. 



Leaf small, thick, eularged abovo the base, rounded downward, narrowed to an obtuse point ; 

 nervation 3-palruate. 



Platanus diminutivus, Lesqx., American Journal of Science and Arts, (2), 



xlvi, 1868, p. 98. 



This small leaf, a little more than 2 centimeters long and nearly as large, 

 may be a diminutive form of P. primaeva or of P. heerii, and even may be refer- 

 able to another genus. It looks like a leaf stunted by parasitical excrescences. 

 It is round from the middle to the base, and broadly deltoid, obtusely pointed, 

 undulate or nearly entire. The impression of its surface is deeply furrowed 

 by the two thick primary lateral nerves, which are slightly alternate, and both 

 like the medial nerve, and the secondary veins are thickened here and there 

 by irregular bolsters or expansions. The primary veins alone are branch- 

 ing; the nervilles are thick, continuous, perpendicular to the veins; the base 

 appears broken, and, therefore, it is not clear if the leaf is prolonged downward 

 along the petiole. 



Habitat. — Dakota group. The specimen had no label. It is mixed with 

 specimens from Lancaster County, Nebraska, and the stone is of the same 

 color and consistence. 

 10 L 



