110 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



The figure given on PL XXXV is that of a complete leaf about half 

 the size, linear, of the largest contained in the collection. 



In texture the leaf was apparently similar to that of P. occidentalism 

 rather thin and more or less roughened. 



Formation and locality: Tertiary (Eocene?). Banks of Yellowstone 

 River, Montana. 



Order ROSACEA. 



Pyrus cretacea Newb. 



PI. I, fig. 7. 



Ann. N. Y. Lye. Nat. Hist., Vol. IX (April, 1868), p. 12; Ills. Cret. and Tert. PI. 

 (1878), PI. II, fig. 7. 



" Leaves petioled, small, roundish-oval or elliptical, often slightly 

 emarginate, entire or finely serrate; medial nerve strong below, rapidly 

 diminishing toward the summit; lateral nerves four or five pairs with 

 intermediate smaller ones, diverging from the midrib at unequal angles, 

 curved toward the summits, where they anastomose in a series of arches 

 parallel with the margin; tertiary nerves forming a network of which the 

 areolae are somewhat elongated." 



Collected by Dr. F. V. Hayden. 



There are a number of leaves in the collection, of which the characters, 

 as far as they are discernible, agree more closely with those of the species 

 of Pyrus than with any other with which I have compared them. All the 

 traces of their original structure which remain, however, are quite insufficient 

 to permit their generic limitation to be determined with any degree of cer- 

 tainty. The leaves of many of the allied genera of the Rosacea? have so 

 much in common that even with the leaves of the living plants it would 

 be difficult, if not impossible, to separate them. The fossils before us are, 

 however, very characteristic of the formation which contains them, and 

 for that reason require notice, and, as far as practicable, description. 



There are several other leaves in the collection which seem to me to 

 have belonged to Rosaceous trees, and there is perhaps no a priori improba- 

 bility that Pyrus began its existence on this continent with its congeners and 

 companions in our forests of the present day. 



Formation and locality: Cretaceous (Dakota group). Smoky Hill, 

 Kansas. 



