1872.] HICKS TREMAD0C ROCKS. 45 



across, blunt at the extremities, and usually more or less incurved, 

 or pressed against one another as if partly rolled up. Tail wide, and 

 more or less truncate. Axis strongly raised, and composed of ten 

 rings, the hindermost being large and pyramidal ; lobes marked by 

 seven strong ribs, grooved towards their extremities, and reaching 

 quite to the margin. The anterior border is deeply faceted where 

 it receives the hindmost thoracic segment. The posterior border 

 widened out, and almost angular at the extremities. This species 

 occurs plentifully, and is at least four or five inches in length. 

 Loc. Ramsey Island, and Tremanhire, near St. David's. 



Neseuretus quadratus, spec. nov. PI. III. figs. 11-13 & 23-26. 



The glabella in this species is rather narrower, more angidar, and 

 less convex than in the other species. Cheeks strougly raised, and 

 deeply punctated, and the margin in front is covered with minute 

 spines. The punctate surface and spinous margin, however, are 

 not specific characters, as they occur also in the larger specimens 

 of N. ramseyensis. 



Of the numerous tails which have been discovered, and which ap- 

 parently belong to different species, I am inclined to believe that the 

 forms figured (figs. 23-26) belong to this species. In these the axis is 

 narrow, the lobes wide, and the hinder border more convex than in 

 Neseuretus ramseyensis. This is probably the largest of the species. 



Loc. Ramsey Island and Tremanhire. 



Neseuretus recurvatus, spec. nov. PI. III. figs. 5 & 6. 



A small species, probably not more than an inch in length. Head 

 wider than the body, and about a third of the whole length; 

 surrounded by a strong and wide margin, which is raised and bent 

 backwards in front of the glabella, and slightly produced at the angles. 

 Glabella occupying more than three fourths of the length, and nearly 

 a third of the width of the head, parabolic and convex in shape, and 

 indented by three pairs of furrows, which are well marked and deep. 

 Eyes large, very prominent, situated halfway up the head, and rather 

 near to the glabella ; free cheeks triangular in shape. 



Thorax composed of thirteen segments. Axis convex, wide at the 

 upper part, and tapering gradually towards the tail ; pleurse deeply 

 grooved, faceted, and incurved at their extremities. 



Tail wide, with a strongly raised tapering axis of eight (or nwre) 

 rings ; lobes ribbed, and margin incurved ; slightly truncate at the 

 extremity. One of the specimens is coiled up, and another partly so. 

 The recurved strong margin to the head, and the long parabolic 

 glabella, distinguish this species at a glance from any of the others. 



Loc. Ramsey Island and Tremanhire. 



Neseuretus ? elongatus, spec. nov. PI. III. figs. 1-3. 



Ovoid in shape, widest across the head. Head semicircular, and 

 equal to about a fourth of the length. Glabella parabolic and con- 

 vex, less than one third the width, and more than three fourths the 

 length of the head. Cheeks equally convex with the glabella. Eyes 



