298 GEOLOGY OF THE ISLE OF WIGHT. 



a sketch of this specimen of the natural size, 

 immediately favoured me with his remarks on 

 this interesting fossil. He considers the speci- 

 men to be the upper termination of a stem of the 

 Clathraria, garnished with persistent leaf-stalks ; 

 and that some of the uppermost petioles were 

 broken off accidentally while the leaves were alive ; 

 but that in the lower ones which possess vascular 

 markings on their summits, the leaves were 

 detached naturally, and these petioles remained, 

 probably for some years, as is the case in the 

 existing Cycadeae. The petioles having fallen 

 from the exposed part of the stem, the surface is 

 left bare, and is marked by lozenge-shaped cica- 

 trices or scars, which are the points of attachment 

 of the bases of the leaf-stalks. 



On the other side of the specimen there appeared 

 to me indications of the foliage, but M. Brong- 

 niart suggests it as more probable, that they are 

 only elongated and flattened petioles. 



The occurrence of this very characteristic plant 

 of the Wealden high up in the chalk formation, 

 is in accordance with the discovery of the bones 

 of the Iguanodon in the greensand of Kent.'* In 

 the strata of Tilgate Forest the remains of the 

 C'lathrariae are invariably associated with water- 



* Wonders of Geology, vol. i. p. 394. 



