§20. 



FOSSIL PLANTS OF THE WEALDEN'. 



393 



show that they have been principally derived from two 

 elegant extinct species of ferns, which are peculiar to the 

 Wealden. The one is cha- 

 racterized by its slender and 

 minutely divided wedge-shaped 

 leaflets (Sphenopteris Mantelli, 

 Lign. 87) ; the other by the 

 distribution of the nervures 

 or veins (Lonchopteris Man- 

 telli, Lign. 88), the long and 

 many times pinnated leaves, 

 and the reticulated disposition 

 of the secondary veins that 

 spring from the mid-rib of the 

 leaflets. This plant has also 

 been found in the valley of 

 Bray, in the lower Boulonnais, 



by M. Graves of Beauvais (p. LlGH 87.-gMw*opraiis Man 

 227) ; and in Sweden, in strata TELLI - tilgate Forest. 

 supposed to be of the same epoch as the wealden. The Lon- 



LlGV. 



-LoNCHOPTERIS MAN TELLI. TlLGATE FOP.EST. 



chopteris likewise occurs high up in the greensand strata, 

 at Atherfield and Shanklin chine in the Isle of Wight.* 



* It was first noticed in this geological position by Mr. John Morris. 

 Geol. Exc. Isle of Wight, p. 230. 



