LOWER HELDERBERG ROCKS. 367 



Pygidium somewhat triangular, excluding the marginal extensions of the 

 ribs. The axis is extremely prominent, occupying about one-third the 

 entire length, rising at its posterior extremity into a rounded boss, 

 from the centre of which proceed two strong spines, with a smaller 

 one on each side, and two in front and behind in the line of the two 

 central ones. Median lobe below the axis prominent, and rising in the 

 middle into a strong node bearing a double spine, and thence sloping 

 abruptly backwards, and deeply bifurcate at the extremity. Ribs broad, 

 extending in strong mucronate processes beyond the sinuosities, Avhich 

 divide them for about one-third of their entire length : the submedian 

 groove extends to the extremities, which are always gently bent up- 

 wards. The inner fold of the marginal limb is extremely thickened 

 and deeply striated. 



Surface pustulose, with short spines on the axis, and on the ribs, in lines 

 parallel to their margins. 



This species differs sufficiently from the preceding, to be readily distinguished 

 tn any of its parts. The median lobe of the glabella is toore prominent, and the 

 J>Q8tulose marking much coarser; the anterior lateral lobes are broader behind and 

 less prominent in front; while the gibbous axis and middle lobe of the pygidium, 

 with the strong prominent spines, are distinguishing features. The extensions of the 

 ribs of the pygidium are likewise narrower, stronger, and more rigid than in the 



preceding si>ecies. 



PLATE LXXVII. 

 Fig. 9. A t)oil.!oB of the head, shotting the median and anterior lateral lobes of ihc glabella. 

 Fig. 10. Lateral view of the same, 

 fig. ll. A fragment of the pygidium, showing a part of the 4Xis and the ribs on one sride. 



Pig. 12. Profile of the same, showing the protuberance at the posterior extfcmity of the 

 axis, from which the spines have been removed ; and likewise the prominence 

 between that and the fextfemity. 



PLATE LXXVIII. 



Fig. 1. A part of the head, showing the median lobe and anterior lateral lobes of the 

 glabella, the occipital furrow and annulation. The specimen has been crushed, 

 and some parts of it arc incorrectly represented. 



Fig. 2 & 3. Fragments showing the lower side of what appear to have been the movable 



cheeks. 

 Fig. 4. The pygidium, which is nearly entire in all its parts, except the protuberance, and 



the spines at the extremity of the axis, which are broken off. The short spines 



towards the posterior extremity are, in this specimen, a little on one side of the 



centtd. 



