10 



this band is much broader than that of a living Zamia, and 

 placed nearer the circumference of the stem. A 

 cortical zone, similar in structure to the centre 

 medulla, surrounds the woody cylinder, and from it 

 spring the leaves, which are supplied with vascular 

 tissue, passing through the cortical cells into the 

 petioles of each leaf in small distinct bundles. 



The petioles encircle the trunk, and are slightly 

 keeled below, the edges are curved upwards, giving the 

 upper surface a somewhat concave appearance. The 

 depth of the zone of petioles exceeds the diameter of 

 the tree, giving it the character of being much larger 

 than it is, its exterior ornamentation looks like trellis- 

 work, the. compartments are disposed spirally, and are 

 seldom filled, the decayed leaves having left a cavity 

 surrounded by the mesh-shaped ridges of the 

 ramentum, which, during the life of the tree, clothed 

 the under surface of the leaves, and distinctly separate 

 each from its neighbours. Some of the most durable 

 may be observed filling up the depressed areas. 



The exterior of the fossil bears three axillary 

 branches, which are associated with the bases of the 

 petioles, and probably supported the organs of repro- 

 duction. Some trunks bear no branch nor bud, which 

 may have been male plants, their staminal flowers would 

 in that case be produced at the termination of the 

 main axis. 



Mantellia nidiformis usually exhibits a deep cavity at 

 its summit ; the apex of the stem being more 

 perishable and longer under the influence of the 



