Mr. Salter on Paleozoic Fossils from South Africa. 217 



even the impressed oval space (fig. 1 c) is granulated. The hypostome is smooth, 

 or nearly so ; but the beak is rough. 



We have two perfect specimens of the body and many fragments. Each of the 

 thirteen rings is convex, almost subcylindrical in its posterior portion, and has 

 generally one large spine on each side at a short distance within the fulcral point 

 (see fig. 1), and none on the pleurse. In other varieties, however, (fig. 5) two 

 spines occur on each side, both within and beyond the fulcrum, and scattered 

 spines appear on the middle part of the axis ; but these are rare exceptions. The 

 fulcrum is but slightly marked, and placed far outwards ; and beyond it the 

 pleurse slope gently outwards for a short distance and then bend abruptly down 

 at a right angle, with a wide and strong facet. Fig. 5. PI. XXIV. represents 

 these pleurse flattened out by pressure ; their true form is indicated in the figure 

 of a more perfect specimen, fig. 4. 



The specimen illustrated by fig. 6, if not a distinct species, is at least a very 

 remarkable variety, with broader segments more deeply trilobate, — the trilobation 

 taking place within, and not at, the fulcral point. It is probably a distinct species. 



The length of the body is not twice that of the tail, and it is rather flattened 

 down the middle. The anterior segments are much arched backwards at their 

 extremities, and the tips of all the pleurse are broad, rounded, and recurved. 



The tail is long-triangular, longer by one-fifth than the width, and so convex that 

 the depth is nearly equal to the width. The axis is highly arched, not so wide 

 as the sides, which are almost vertical, and scarcely marked off at all from them. 

 The tail of the young animal (fig. 8) is shorter and broader, and has fewer ribs. 



The ribs are all continuous across. There are sixteen or seventeen on the axis 

 of our largest specimen ; and the front seven or eight of these have tubercles on 

 each side, and a few tubercles also down the middle. About ten or eleven show 

 themselves distinctly on the sides ; but the lowest ones are faint, and more arched 

 forwards than the rest. A few only of the upper ones bear any tubercles at the 

 base. Occasionally there are more tubercles. 



The apex is blunt-pointed, and a little abruptly produced from the tip of the 

 axis, which reaches nearly all the way down. 



The incurved margin (fig. 7 c) is not broad ; and, like the whole of the upper 

 surface of the tail, is rough with granulations. The anterior facet (see fig. 7 h) is 

 large and sharply defined. 



This species differs at a glance from the related species H. armatus, Burm., in 

 the much larger glabella and broader axis of the body. The tail, in proportion to 

 the body, is twice as long; has double the number of rings ; and ends in a blunt 

 short point ; while in H. armatus it is a prolonged spine. Nor do we know of 

 any other published species of at all similar character, except H. Pradoanus, De 



2 g2 



