92 



The angle of" divergence of the secondary veins is also variable. Leaves of 

 H helix, L., the European ivy, have been found fossil in the Tertiary of Italy. 

 Gaudin (in Contributions, etc., Ill, p. 17, PI. i, Figs. 21-24) describes, under 

 this name, leaves closely related by form and nervation to those of the Dakota 

 group. 



Habitat. — Near Decatur, Nebraska. The specimen of PI. xxiv, Fig. 4, 

 is from Kansas, Mudge. 



POLYCARPIC/E. 



Magnolia tenuifolia, Lesqx., PI. xxi, Fig. 1. 



Leaf large, oblong, rounded upward to an obtuse point('), (broken,) narrowed in a curve to a short, 

 slender petiole ; medial nervo straight, narrow ; lateral veins alternate, on a broad angle of divergence, 

 slender, undulate, deflexed near their point of insertion to the medial nerve. 



Magnolia tenuifolia, Lesqx., American Journal of Science and Arts, loc. cit., 



p. 100. 



The upper part of this leaf is destroyed ; it is a large leaf of thin texture, 

 about 17 centimeters long, 7 centimeters broad, oblong oval, entire or undu- 

 late on the borders, apparently rounded upward to an obtuse point, gradu- 

 ally curving to the petiole, which, like the medial nerve, is rather slender, at 

 least for a leaf of this size. The secondary veins mostly opposite, irregular 

 in distance, or obliterate here and there, are very thin, on a broad angle 

 of divergence of 60°, undulating to the borders, where they curve, and which 

 they appear to follow. 



The relation of this leaf with that referred to Persea leconteana has been 

 remarked upon in describing this last species. 



Habitat. — Decatur, Nebraska ; represented by four specimens. 



Magnolia alternans, Heer, PI. xviii, Fig. 4. 



Leaves coriaceous, ovate-oblong or elliptical, entire, tapering to the petiole; secondary veins nu- 

 merous, parallel, camptodrome, at an acute angle of divergence. 



Magnolia alternans, Heer, Phyllites, p. 20, PI. iii, Figs. 2-4 ; PI. iv, Figs. 

 1-2. — Lesqx., American Journal of Science and Arts, loc. cit., p. 100. 



The leaf figured in this memoir is not as perfect as those which Profes- 

 sor Heer had for his description of this species. Our figure is comparable in 

 size, form, and nervation to that of PI. iii, Fig. 3, of the Phyllites, which has 

 the base of a leaf with a short, slender petiole, while the upper part and the 

 base of ours is broken. In both these leaves, as also in the fragment repre- 

 sented, (PL iv, Fig. 1, of the same memoir,) the secondary veins appear 

 intermixed with shorter tertiary ones. This character, like the form of the 



