LOWER HELDERBERG ROCKS. 3G3 



Area between the lenses marked by a small round granule at each 

 angle of a hexagon which circumscribes the lens. 



Htpostoma 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 0131 

 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 th^ 

 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 po.sterior extremity, 

 as measured in one specimen which appears to be entire, is al^Q^it flftce 

 and a half as long as the pygidium. 



Surface of the head, annulations, ribs and marginal limb of the pygidium 

 pustulose, with intermediate finer granulose markings ; the spine 

 somewhat more coarsely granulose. 

 This species is remarkable both for the bifurcate rostration in front of ^he head, 



ui4 for the long posteri ir spine. The test is perhaps a little thicker than tliat of 



