296 GEOLOGY OF THE ISLE OF WIGHT. 



one to two inches wide, rounded above, and con- 

 tracted below, as shown in the detached petiole 

 figured in lign. ~1< ; they are traversed by fine 

 and nearly parallel longitudinal veins. The sum- 



LIGN. 24. A PETIOLE OF CLATHRAR1A LYELLII, SEPARATED FROM 



THE STEM. 



a, the external aspect ; 



b, the internal surface ; 



c, the vascular markings left on the summit of the petiole 



by the separation of the leaf. 



mits of those petioles from which the leaves 

 appear to have been shed, not broken off, arc 

 marked by vascular pits disposed with great 

 regularity, as shown at c, lign. 24 ; a structure 

 which M. Adolphe Brongniart informs me partakes 

 more of the character of the Ferns, than of the 

 Cycadeae. The substance of this fossil is a sandy 

 marl, and probably does not retain any traces of 

 the internal structure of the original ; still it is 

 desirable that sections of the petioles, and of 

 the stem, should be microscopically examined. 

 M. Adolplic Brongniartj to whom 1 transmitted 



