46 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 4, 



semilunar in shape, and situated more than halfwaynp the head; the 

 anterior facial sutures run upward and slightly outward, the posterior 

 bend first under the eyes, and then run obliquely outward to the 

 inner side of the posterior angles. Thorax composed of thirteen seg- 

 ments ; axis strongly raised, rather narrow, in width equal to rather 

 less than two thirds the length of the pleurae. Pleurae deeply grooved, 

 faceted, and blunt at the extremities ; fulcrum in the upper ones 

 situated at about a third of the distance from the axis. Tail semi- 

 circular, and margined ; axis well raised, tapering, and composed of 

 eight segments ; lobes strongly ribbed at the upper part, but very 

 faintly so posteriorly. 



This may possibly belong to another genus ; but as some of the 

 characters are those of Neseuretus, I prefer at present to retain it 

 under that genus. 



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



Niobe menaptensis, spec. nov. PL IV. figs. 1-9. 



Oval in form, from 7 to 8 inches long, and about 3 inches wide. 

 Head one third of the whole length ; in shape longer than a semi- 

 circle, strongly margined, with long tapering spines reaching back- 

 wards at least two thirds of the length of the thorax. Glabella 

 occupying one third of the width of the head, and reaching forward 

 to the anterior margin, which it partly indents ; wide in front, and 

 posteriorly, and contracted at the middle third. It is indented by 

 five or six faint and short furrows on each side, and by a well- 

 marked neck-furrow. Eyes near the glabella, and placed more than 

 halfway up the head. The anterior facial sutures run obliquely 

 outwards, above the eyes, and cut across the margin at a distance 

 from the glabella equal to about a third of its width. The 

 posterior sutures curve sharply backwards, and outwards, across the 

 posterior margin, near its middle. Thoracic axis wide, about the 

 width of the pleurae anteriorly, but tapering gradually backwards. 

 Pleurae deeply grooved, with the fulcrum situated at about one third 

 of their length from the axis ; they are strongly faceted, and very 

 slightly pointed at their extremities. 



Tail semicircular, with a very broad margin; axis moderately 

 convex, and marked by ten distinct rings. The tip is prominent, and 

 bluntly pointed. The sides narrow, and scored by eight furrows, 

 which are interlined, and reach to the edge of the broad margin. 

 (In one specimen they seem partly to run across the margin.) The 

 margin is concentrically striate, about equally wide throughout, and 

 raised on the inner side above the level of the surface of the lobes. 

 Labrum long, and slightly pointed, with a strong concentric furrow 

 near the posterior margin ; the margin is wide, and indented by a 

 pair of furrows near the tip. "Width, equal to about two thirds of 

 tbe length. Front much arched and about equal in width to the 

 posterior portion. 



This magnificent species is considerably larger than the Niobe 

 Homfrayi, which occurs in North Wales, and differs from it in many 

 particulars, though not sufficiently so to form a new genus. Niobe 



