416 



ON SPECIES OK FOSSIL PLANTS 



broader more distinctly undulate leaves, with a more abruptly narrowed base, as in Fig. 

 2. The primary nerve is of medium thickness ; the angle of divergence of the secondary 

 ones is about 50°. In our specimens the secondary nerves arc generally opposite from 

 the base of the leaves up to the middle, a character marked also in Heer's Fig. 6. They 

 nearly reach to the borders, where they fork, the upper branches running along the bor- 

 ders and muting to the next. The areas arc divided into secondary ones by continuous, 

 sometimes forking veinlets, forming a kind of irregularly polygonal reticulation, which 

 still incloses a more delicate subquadrate one. Prof. Heer points out the relation of this 

 fossil oak to some species now living in Mexico: Quercua Xalapensift, Thunb., Q. undulata, 

 Web. This type has many representatives in the Miocene of Europe. 



10. Quercus retiiacta, Spec. nov. PL xvi, Figs. 4, 5. Q. foliis coriaceis, politis, obovatis, oblongis, vel 

 lineari lanoeolatis, integerrimis; ncrvo prcmario piano, recto; secundariis tenuibus, horissontalibus vel retro curva- 

 tis, camptodroiuis imperfectis, arcis abrcviatis. 



Red shale. 



I have figured the only fragments, though small, found of this species. By the form 

 of the leaves, evidently very variable, and by its pccidiar nervation, it has a marked rela- 

 tion to our living Quercus aquatica, Catesb., of the Southern States. With generally 

 obovate or oblong lobed leaves, this oak has also narrow linear entire leaves, whose nerva- 

 tion is scarcely different from that of the fossil species as marked Fig. 4 a. Quercus eloena, 

 Heer, of the (Eningen stage of the Tertiary of Europe, is also closely related to the Mis- 

 sissippi species. It may be identical, but our specimens are too incomplete to allow a 

 satisfactory comparison. 



11. Quercus Chiobophylla, Ung. PI. xvii, Figs. 5, 6, 7. Q. foliis coriaceis, ovatis, oblongis, obtusis, vel 

 apice rotundatis, quando que sub-emarginatis, integerrimis, margins rcflexis, nervis secundariis tenuibus, obsoletis, 

 cainptodromis, angulo acuto egredientibus. 



Red shale. 



As far as can be ascertained in comparing fossil leaves whose nervation is undiscerni- 

 ble, our species is identical with the one described under the above name by Prof. Unger, 

 Chlor. Pro tog., page 111, PI. xxxi, Fig. 1. However, it is not certain that these leaves 

 belong to an oak. Oval, thick, entire coriaceous leaves of the same form as ours are found 

 in different genera of living plants. The author compared this species to Quercus imbri- 

 caria, Mich., Q. einerea, Mich., and Q. virtus, Ait. But all these species of ours have a 

 well-marked nervation, and their leaves are thinner or less coriaceous. 



12. Celtis hrevifolia, Spec. nov. PI. xx, Figs. 4 and 5. C. foliis ovatis, acutis, vel acuminatis, brevibus, 

 integerrimis, basi rotundatis, latere uno latiore intequalibus, nervo medio recto, secundariis distantibus, oppositis, 

 imperfecte acrodromis, nervulis subcontinuis, parallel!*. 



