with. Descriptions of X. w Species of Fossil Pla 



tremities prolonged parallel with the margins of the leaf; the upper 

 ones strongly arched, but terminating more directly in the margins; 



tertiary nerves distinct, mostly simple, straight, and parallel among 

 themselves, connecting adjacent secondary nerves nearly at right 



angles. 



The form, serration and nervation of these leaves are entirely 

 those of Carya, and while without the frnit it maj not be pos- 

 sible to fix their place in the series more definitely than to Bay 

 that they represent the genus Juglans as formerly coi 

 tuted, including Carya, we may at least refer them with con- 

 fidence to a place within the limits of that genus. The lea 

 of the species of Carya and Juglans arc very Bimilar : BO much 

 so that some of the Caryas, such as C. oUvaformis, have 

 leaves that could in the fossil state hardly be distinguished 

 from those of Juglans. 



The specimens before us, however, seem to me to be more 

 widely separated from those of the known species of Jugl 

 than are those of the Pecan ; and there seems little donbt that 

 the tree if now living would fall within the limil I arya. 



In some specimens, the lateral nerves are remarkably straight 

 and numerous, giving to the leaf very much the aspect of those 

 of JEsculus ', but from a comparison of the many leaves of thi- 

 plant in the collection of Dr. Hay den, I infer that they w 

 not palmately grouped, but pinnate, the form of the bases of the 

 leaves indicating this. 



The tertiary nervation is also quite different from that 

 JEsculus. In the latter genus it usually forms an i 

 ingly fine network filling the interspaces between the second- 

 ary nerves, in which the straight transverse lattice-like ' 

 characteristic of the fossils before us arc wanting. At l< 

 tliis is the case with our American "Bucl 1" -A! // 



pocastanum of the Old World something of the kind 

 but in prevalence and regularity very unlike that in the I 



Formation in, <l Locality. Tertiary -Tata. Month of \ 

 lowstone River. (Dr. Bayden.) 



