

( 88 MR- W. C. WILLIAMSON ON THE HISTORY OF ZAMIA GIGAS. 



demonstrates the shape of the pyriform axis, and also the abrupt way in which it termi- 

 ii,;: b superiorly on the detachment of the organ which it sustained. 



I ■-. 5 represents a specimen closely resembling fig. 7, but giving us additional facts ; 

 it exhibits, in the interior of the pyriform peduncle, a cylinder of carbonaceous matter 

 having well-defined boundaries. This cylinder appears to have been separated from the 

 surrounding cortieal cells by a narrow interval, which may have been occupied by some 

 different kind of tissue; its inner surface exhibits strongly marked longitudinal parallel 



moves, which extend upwards into the constricted part of the axis. This cylinder 

 bean the aspect of a woody zone, of which the longitudinal ridges represent vascular 

 bundles; but if so, the vessels have been much more densely packed, as well as more 

 i ;ularly parallel to each other, than in recent Cycads. 



This specimen, belonging to Mr. Kipley, also affords indications of the extension of 

 the pyriform axis beyond the usually terminal funnel, and shows that the latter became 

 suddenly contracted by a curious inflexion of the tissues composing it, and further indi- 

 cat< that the centre of the lenticular disk thus formed has been extended upwards into a 

 c< it ml prolongation. Two invaluable specimens in my own cabinet confirm and further 

 illustrate this part of the structure. One of these contains the pyriform axis detached 

 from the involucrum; on splitting the specimen, in order to trace its upward prolonga- 

 tion, I obtained the conclusive results indicated (double the natural size) in figs. 7, 8, 

 md 9 (Plate LI 11. ), demonstrating the actual termination of the axis. The last two 



o 



fi ur - rep re int the two halves of the specimen, showing the upper extremity of the axis : 

 the pyriform dilatation does not appear in the drawings, being on the reverse side of the 



fra ment indicated by fig. 8 ; but fig. 9 exhibits the appearance this specimen would 

 have presented had the fracture happened to pass through the central plane of the speci- 

 men. In Bg. 8, as just stated, the pyriform axis is imbedded in the stone. It differs 

 from all the other examples I have seen in having the interior surface of the hollow cast 

 marked by numerous irregular longitudinal rugae. As the specimen has no traces of the 

 involucrum attached to it, and as it is the only one in which I have found the surface of 

 tin part of the axis otherwise than smooth, I think we may attribute these ruga? to the 

 partial iirivelling of the organism prior to its fossilization. At the base of fig. 10 we 

 i B mall portion of the grooved funnel, the striated surface of which only extends 

 about half the distance between its outer margin and the constricted part of the pyri- 

 for axis below. From this margin the axis rapidly contracts superiorly, in the way 

 f sented in ng. 7, demonstrating that the funnel-shaped structure was the inferior 

 part of a disk, to which I would apply the name of the lenticular disk. Inferiorly, the 

 surface of this disk has been concave, and convex on its upper surface, the central 

 portion of the latter being further prolonged into a pyramidal structure about an inch 

 in length. This structure may be designated the pyramidal axis ; its surface is indented 



with numerous longitudinal grooves and stria, very similar to those on the 



surface ol the lenticular disk, but not quite so strongly defined. In fig. 10, some of 



^ , longitudinal grooves are more deeply indented than others, and J. „ 



the opposite side of the pyramid represented by fig. 8. Near its upper 



in f e r 



not seen 



this differ 



"'c pyramidal axis again expands into a cup-shaped enlargement about 





