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. Itibs broad, 
extending in strong mucronate processes beyond the sinuosities, which 
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 
in any of its parts. The median lobe of the glabella is< more prominent, and the 
pustulose 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 species. 
PLATE LXXVII. 
Fig. 9. A portion of the head, showing the median and anterior lateral lobes of the glabella. 
Fig. 10. Lateral view of the same. 
Fig. 11. A fragment of the pygidium, showing a part of the axis and the ribs on one side. 
Fig. 12. Profile of the same, showing the protuberance at the posterior extremity of the 
axis, from which the spines have been removed ; and likewise the prominence 
between that and the extremity. 
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 are 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 arc, in this specimen, a little on one side of the 
centre; 
