• MR. W. C. WILLIAMSON ON THE HISTORY OF ZAM1A GIGAS. 667 



annular area of radiating cells. Since the drawing fig. 5 was made, the sp< inien repn - 

 sented has been accidently reduced to the common form, the central portion having 

 fallen out. It now, like figs. 5 & 7, shows a central cavity, bounded inferiorly l>y the 

 concave annular area. 



The central cavity swells out into a pyriform space once occupied by an expansion of 

 the axis, contracting again towards its upper part, its greatest diameter being at about 

 its lower third. The interior of this cavity is perfectly smooili in the specimen in ques- 

 tion. Above the contracted upper extremity it developed into a structure which a 

 second casual fracture revealed after the drawing was made, and to which I shall call 

 attention in connexion with another specimen. 



Fig. 7 represents a specimen in which the inferior central portion has become detached. 

 The frequency of this occurrence would have misled me respecting the thickness of tin 

 axis at this point, but for the solitary example described; I should have considered that 

 part of the axis to have had, not only a diameter several times greater than lias actual!} 

 been the case, but that it had a convex extremity fitting into the concavity fanned by 

 the radiating structures represented in fig. 7. The base of fig. 7 exhibits two concentric 

 circles, the intervening concave area being occupied by numerous small radial in- 

 elongated cells* arranged vertically upon the axis; the inner circular margin forms 

 the margin of a large pyriform cavity left by the removal of the axis. I would designate 

 this latter portion of the structure the pyriform axis. As in the case of the prei iotu 

 specimen, this cavity contracts superiorly, terminating in a narrow circular apert 



Tin- 



this example, from the Scarborough Museum, also indicates that the outer surface of the 



pyriform axis has been perfectly smooth. 



Pig. 3, a specimen in my own cabinet, carries us a step further, showing the superior 

 constricted part of the pyriform axis expanding into a funnel-shaped appendage, the 

 surface of which has been strongly marked with parallel longitudinal lines, 

 are due, as other specimens demonstrate, to « cells " like those seen at the base oi the 

 involucre (fig. 7), but differently arranged, being parallel to the surface ot the axis and 

 not vertical. This new arrangement will be demonstrated from other examples. 



In nearly all the specimens hitherto discovered, the central axis terminates at the 

 margin of this funnel, which is sharply defined, and at which the diverging groov,, end 



abruptly. That this structure had supported some additional appe^agc Mippe*ed 



obvious to me ; but years of research passed by before I obtained the slightest clueto «« 

 missing parts. That it had been deciduous, or at all events very ^^"££ 

 at this point, was sufficiently obvious, since of the dozens that I «»^^ 

 a trace of the terminal organ. A specimen represented in fig 4 BJ^JJ^jJ 



lnvnnnr.,,^ „„,i ;±„ ~,™;p™,™ nvic through its cenue, auu^x a 



mvolucrum and its pyriform axis through its cenue, *u 



solid and not a hollol structure; all its vegetable carbon is F»«^»** 



an 



amorpl 



. nouow su-uciuie , a u- ^ S(nr broite so commonly found 



i<4 PrmdiHnr, intersected with bands oi the fceaiuiouo a * 



as condition, mteisecieu wit M „j fl *nnea This specimen admirably 



the vegetable remains of these Yorkshire sandstones. 1 



cavities, because I can find no better, but without any evidence 



a »u mc v^ 



* I shall use this word to represent these curious 

 that the expression is applicable here in its physiological sense. 



