82 Heign of Angiosperms. 



those of the Chalk, properly so called, and none whatever with 

 those of the most ancient beds of the Tertiary formations, 

 such as those of Monte-Bolca. 



" From the study and comparison of these fossils, derived 

 from such various sources, we may divide the Cretaceous period 

 into three epochs, of which the middle one is the true Creta- 

 ceous epoch. The others, characterised almost exclusively 

 by marine vegetables, are somewhat doubtful with regard 

 to their true geological position ; the one, more ancient than 

 the Chalk, contains only the subcretaceous lignites of the 

 neighbourhood of La Rochelle, and the Department of Dor- 

 dogne ; the other, superior to the Chalk, corresponds to the 

 Sandstone with fucoides." 



The subcretaceous epoch comprehends Algse, Naiadese, 

 and Coniferee. 



" This small Flora is almost entirely founded on fossil 

 plants, collected among the marine lignites of the Isle of Aix, 

 near La E-ochelle, long since described by M. Fleureau do 

 Bellevue. 



" The difference of the vegetables does not appear to admit 

 of connecting this Flora with that of the inferior chalk or 

 greensand ; but it would require to be more completely ex- 

 amined, both with regard to its precise geological epoch and 

 the entire amount of vegetable species which it contains. 

 The most abundant and characteristic of these species is the 

 Bhodomelites strictus^ whose branches, crossed and mingled 

 with Zosterites, constitute the mass of these lignites with the 

 wood of Coniferse, which have not yet been studied, and small 

 branchlets, very rare, of Br achy phy Hum orbignianum. 



" I have referred to this period the two Cystosciri'es, de- 

 scribed by M. de Sternberg, and mentioned by him as found 

 in the beds between the Jurassic slates and the chalk in 

 Transylvania. 



'* Does this fossil Flora correspond to a formation almost 

 entirely marine, but cotemporary wdth the Wealdean epoch % 

 New investigations can alone determine this, but we may 

 suppose an analogy between the Brachyphyllum of the two 

 epochs." 



2d, Cretaceous Epoch. — The Cretaceous epoch presents us, 



