LOWER HELDERBERG ROCKS. 369 



joining the frontal border, and forming with it a continuation of a 

 similar border ; the pustules, as they recede from the centre in front, 

 gradually become stronger and assume the form of short spines, which, 

 to the number of ten to fourteen, ornament the cheek border. The 

 posterior angle is produced in the form of a long curving spine, on the 

 inner margin of which, beyond the limits of the head proper, are one, 

 two, or three short spines. 



Eyes nearly in a line with, or a little in advance of, the occipital furrow, 

 subcylindricelly ovoid ; showing, under a lens, the minute facets upon 

 the surface. 



The thorax (imperfect) has apparently nine segments : the axis is very 

 prominent, and nearly one-third narrower than the lateral lobe ; the 

 articulations marked by a node at each extremity, and one in the 

 centre : lateral lobes of the axis having the articulations produced into 

 a long rounded spine, which is bent abruptly backwards, and finally 

 assumes a direction nearly parallel to the axis ; each of the articula- 

 tions marked by two strong nodes, one of which is at the point of 

 retrorse bending of the rib, and the other nearer to the axis. The 

 prolongation of the spine is two and a half to three times as great as 

 the width of the lateral lobe. 



Pygidicm, excluding the spines, somewhat semicircular, preserving three 

 annulations in the axis, and marked posteriorly by a strong elevated 

 rim. From the middle segment are produced two long spines at right 

 angles to its direction, or parallel to the axis, and, between these, 

 two shorter intermediate spines ; while on each side, exteriorly to the 

 long spines, are three others : the inner one is essentially parallel to 

 the long spines, while the outer ones are divergent, and originate in a 

 bifurcation of the rib. The middle annulation is marked by three nodes 

 in its central portion ; while the long spines each have two strong 

 nodes near their origin, and similar smaller nodes mark the origin of the 

 outer spines. The posterior segment has two small nodes on each side, 

 with the centre plain. 

 [ Pal^ontolooy III.] 47 



