202 M. Brongniart on the Periods of Vegetation. 



Conifers. 

 Brachyphyllum Germari, Brong. — 



Germany. (Thxiites Germari, 



Dunk.) 

 ? Kurrianum, Brong. — Germ. 



(Thuites Kurrianus.) 

 imbricatum, Brong. — Germ. 



(Thuites imbricatus, Rom.) 

 Gravesii, Brong. — Beauvais. 



(Moreausia Gravesii, Pomel.) 

 JuniperitesStembergianuSjJBroK^. — 



Germany, (Muscites Stemberg- 

 ianus, Dunk.) 

 Abietites Linkii, Dunk. 



Plants of Doubtful Class. 



Carpolitbes Mantelli, Stokes. — En- 

 gland, Germany, Beauvais. 



Lindleyanus, Dunk. — Germ. 



cordatus, Dunk. — Germany. 



Brongmarti,X)«MA:. — Germany. 



Sertum, Dunk. — Germany. 



This list is principally derived from discoveries made in recent 

 years in the Wealden districts of the north of Germany, at Oster- 

 wald, Schaumburg, Buckeburg, Oberkirche, &c., the fossil plants 

 of which were first described by M. Romer, and subsequently 

 more completely by M. Dunker, in his monograph on these di- 

 stricts. To these species are added the less numerous and less 

 varied formerly discovered in the Wealden of England, near Til- 

 gate and Hastings Forests, in Sussex, and so well described by 

 Dr. Mantell. 



This same formation has been found in France, near Beau- 

 vais, by Mr. Graves, who observed in it Lonchopteris Mantelli and 

 some other plants, of which I have not seen specimens, and which 

 I have cited from his work on the geology of the department of 

 the Oise. 



The species, to the number of sixty-one enumerated above, 

 appear to be all peculiar to this formation, with the exception 

 perhaps of Baiera Huttoni, which seems identical with the spe- 

 cies of the lias of Bayreuth and of the Scarborough oolite ; but 

 their generic forms are almost all the same as those of the lias 

 and the oolitic formations. Nevertheless the Cycadese already ap- 

 pear less numerous in proportion to the Ferns. 



It will further be remarked that this freshwater formation, 

 which terminates, for us, the kingdom of the Gymnosperms, is 

 allied by its total character to other epochs of the vegetation of 

 the Jurassic period, and is distinguished from the cretaceous 

 epoch which succeeds it, by the complete absence of every spe- 

 cies which can be referred to the angiospermous Dicotyledons, in 

 France and England as in the deposits of southern Germany, so 

 rich in variety of species. On the other hand, in the lower chalk, 

 the upper greensand, Quadersandstein or Planerkalk of Germany, 

 we immediately find several kinds of leaves evidently belonging 

 to the great division of angiospermous Dicotyledons, and some 

 remains of Palms, of which, on the contrary, no trace appears in 

 the Wealden deposits. 



I have classed among the Cycadese the stems from Tilgate 

 Forest, previously called by the name of Clathraria Lyellii, and 



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