DESCRIPTION OF SrECIES. 63 



The nervation of this leaf is of course modified according to its shape, 

 but is not specifically distinct. No. 474 of the collection. 



13. Betulites Westii var. crassus. 

 PI. V, Figs. 15-17. 



Leaves coriaceous, of various forms, round, (»1)tuse or deltoid, acute, 

 cuneate or truncate at base; nervation thick; secondaries simple or ramose;, 

 borders distinctly, even sharply, denticulate. 



Although these leaves, which have been obtained from another locality, 

 differ especialh" in form and could thus be referred to three different species, 

 yet the analogy remarked between all those described as />. Westii, shows 

 that they have in their characters such differences only as can be considered 

 varietal. The coriaceous substance of these three leaves and the thick 

 nervation might, however, be regarded as constituting specific differences. 

 Nos. N, K, B. 



14. Betulites Westii var. populoides. 



The form of the leaf is like that of a Populus, being truncate or sub- 

 cordate at base, much enlarged in the lower part, where it becomes rounded 

 and tapers rapidly to the apex. The nervation is tliat of Betulites Westii var. 

 subintef/rifoliKS, but the lowest pair of secondaries is basilar, the others par- 

 allel, all running straight to the borders, which they enter craspedodrome, 

 being mostly simple, except the lowest pair. The leaf is an impression of 

 the upper surface and is somewhat obscure. 



15. Betulites Westii, var. gbewiopsideus. 

 PI. LXIV, Fig. 10. 



A fine, small round leaf with the nervation of Grewiopsis orhiculata 

 Sap.^ The teeth of the border are somewhat longer and more distinct than 

 the leaf from Kansas. As the same character of nervation is observable 

 upon some of the leaves which I have referred to Betulites, and as the 

 petiole, which is rigid, 1.5"° long, bears at its base a short-pointed stipule 

 like that described in leaves of Betulites, the reference to this genus is 

 authorized. 



Habitat : Ellsworth County, Kansas. No. 1205 of the collection of Mr. 

 R. D. Lacoe. 



' Fl. Fobs. Suzanne, j). 411, PI. XI, Fig. 12. 



