59 



entire slightly undulate borders; lowest primary nerves thin, following the 

 borders, the lateral oblique, (50°) parallel, branching; divisions running to 

 the borders; nervilles in a right angle to the nerves and their divisions, 

 distant and distinct, nearly continuous. The areolation of this species is of 

 the Platanus or Dombeyopsis type. Schimper (Pal. Veget., p. 704) considers 

 it as related to this last genus. 



Habitat. — Near Lancaster, South Nebraska, Hayden. 



Populites elegans, Lesqx., PI. iii, Fig. 3. 



Leaves broadly oval or nearly round, narrowed by an abrupt curve to a long slender petiole ; borders 

 entire, undulate ; nervation pinnate, the lowest secondary veins from above the border of the leaf. 



Populites clegans, Lesqx., Journal of Science and Arts, he. cit., p. 94. 



A well-preserved entire leaf of the same thickish, but not coriaceous, 

 substance as the former, 8 centimeters broad, 10 centimeters long, exclusive of 

 the petiole 2£ centimeters, round in outline, more enlarged below the middle, 

 very obtuse, pinnately nerved ; angle of divergence of the veins 40°; areolation 

 and divisions of the veins of the same type as in the former species. This leaf 

 has not the basilar primary nerves remarked in the former, and the lowest 

 pair branches opposite from above, the base of the middle nerve. These 

 differences, and the form of the leaf, separate it evidently. 



Habitat. — Decatur, Nebraska, Hayden. 



Populites cyclophylla, Heer (?) PI. iv, Fig. 5, and PL xxiv, Fig. 4. 



Leaves round, entire or slightly undulate, rouuded or truncate to the petiole ; texture rather thin ; 

 nervation pinnate from the base ; lateral veins straight, simple, or the lowest only branching, craspe- 

 dodrome. 



Populus cyclophylla, Heer (?), Proceedings of the Academy of Natural Sci- 

 ences, Philadelphia, 1858, p. 266. — Lesqx., American Journal of Science 

 and Arts, loc. cit., p. 93. 



From the short diagnosis given of his species by Professor Heer, I con- 

 sidered this as identical to it. From the observations of the author, however, 

 it is probable that I am mistaken in this supposition. The leaves represented 

 by many specimens are all nearly round, 6 to 7 centimeters wide each way, 

 either abruptly rounded to the petiole or truncate at base, the border 

 slightly inclining downward at the point of contact with the petiole. The 

 nervation is pinnate from the base of the leaves, the lateral veins, five pairs, 

 at equal distance, parallel, all simple except the lowest, passing up from the 

 medial nerve at an angle of divergence of 40° and reaching the borders without 



