LOWER HELDERBERG ROCKS. 3«3 
/ 
Area between the lenses marked by a small round granule at each 
angle of a hexagon which circumscribes the lens. 
Hypostoma hastate; central portion somewhat transversely lobed, the 
points of muscular attachment strongly marked : lateral border sinuate, 
with a short central process at the extremity and three similar shorter 
ones on each side. Thorax unknown. 
Pygidium somewhat triangular, with the sides and articulating face curved, 
the posterior extremity produced in a long slender spine : surface 
broadly convex. Axis prominent, gradually attenuate; width at the 
upper extremity more than half as great as the lateral lobe, marked by 
about sixteen or seventeen annulations, the posterior ones of which are 
subangular in the middle, and the anterior ones marked by a node on 
each side of the centre. Lateral lobes marked by about twelve or thir¬ 
teen ribs, which are wider than the spaces between : ribs marked by 
a narrow longitudinal groove, which, beginning nearer to the lower 
side, runs a little diagonally, so that at a point half the length of the 
rib it is nearer the upper margin, and continues thence parallel to the 
margins till the rib and groove are merged in the thickened border. 
Each of the ribs, about half way from the axis to the margin, is bent 
a little more suddenly downwards, rising again beyond so as to leave a 
shallow depression parallel to the outer margin, the limits of which are 
more or less distinctly marked by a node on one or both sides; and 
when there is no distinct node, there is usually a thickening of the rib 
at the same point. Sometimes there is a line of nodes only on one side 
of the depression in the ribs. These nodes, when developed, interrupt 
the longitudinal groove of the rib. The spine at the posterior extremity, 
as measured in one specimen which appears to be entire, is about once 
and a half as long as the pygidium. 
Surface of the head, annulations, ribs and marginal limb of the pygidium 
pustulose, with intermediate liner granulose markings; the spine 
somewhat more coarsely granulose. 
This species is remarkable both for the bifurcate rostration in front of the head, 
and for the long posterior spine. The test is perhaps a little thicker than that of 
