FROM THE TERTIARY OP THE STATE OF MISSISSIPPI. 



413 



base, and the secondary nerves come out of them and fork in ascending, being generally 

 straight in the middle part of the leaves, and arched on both sides, a nervation somewhat 

 similar to that of some Cyclopteris of the coal measures. In Salisburia adianlifolia, 

 Smith, from Japan, the only living species with which I am acquainted, the primary nerve 

 appears as if split in two branches, which form the two margins of the leaves, and from 

 which the secondary nerves ascend in forking. Another fossil species of Salisburia has 

 been collected by Dr. J. Evans at Nanaimo, Vancouver's Island, in fragments too incom- 

 plete for a satisfactory comparison. None have been described from the Tertiary of Eu- 

 rope. There is one known from the Pliocene of Italy. 



4. Populus monodon, Spec. non. PI. xv, Fig. 1 and 2. P. foliis longis, latisque, lamina sexpolicari et ultra, 

 deltoideo aouminatis, margino undulatis, vol para: irregulariter obtuse lobatis, nervo medio crasso, ncrvis lateralibus 

 apertis, arouatis. 



lied shale. 



This plant is represented only by the two specimens here figured ; and as the base of 

 the leaves is not preserved, the essential character, viz., the basilar nervation, cannot be 

 taken into account. The large ovate or deltoid lanceolate acuminate leaves are probably 

 rounded or cordate at the base, and have the borders either entire or undulate, or marked 

 with a single obtuse lobe. The medial nerve is pretty thick, and the secondary ones are 

 joined to it in an open angle and arched. 



By its nervation and the size of the undulate scarcely lobed leaves, this species is closely 

 related to Populus Oaudini, Iicer, whose leaves are also entire or marked with a few round 

 teeth. The European species differs only by its proportionably narrower and longer acu- 

 minate leaves. 



5. Populus mutabilis, var. repanpo-crenata, Beer. PI. xviii, Fig. 4, 5, 6. P. foliis longe petiolatis, 

 ovato elliptiois, lanccolatis, basi cuneato attenuates, margino ropando cronatis, nervo medio crasso, nervis lateralibus 

 sub-ourvati.s. 



Red shale. 



Though the whole form of the leaves cannot be seen from the fragments found and 

 figured, all the appreciable characters refer these fossil leaves to the species described by 

 Prof. Heer, Flor. Tert. Ilelv., II, page 22, PL lxi, Pig. 12, 13, 14, and PI. Ixii, as one of 

 the varieties of his Populus mutabilis. The broad medial nerve, the long petiole, the 

 crenate-lobed borders of the leaves, and the disposition of the secondary nerves are alike. 

 Both leaves represented in our Pig. 4 are obscure. The long petiole is flattened and the 

 secondary veins are indistinct, or rather look as if they had been split by maceration. As 

 much as can be seen from the fragments, the leaves were of large size, ovate-lanceolate, 



