176 rRoci:EDiKGs or the geological society. 



shape, and divided about its anterior third bj a transverse furrow 

 into two lobes. The anterior lobe is almost triangular in shape ; and 

 it differs in this respect from any other of the Menevian species. A 

 pair of small triangular lobes lie at the base of the glabella. The cheeks 

 are covered with rather strong tubercles. Thorax undeterminable. 



The axis of the tail wide, somewhat pyramidal in shape, and 

 indented by three furrows on either side. The anterior furrows 

 are short and run obliquely inwards, marking oif somewhat trian- 

 gular lobes on either side. The other furrows extend across, and 

 bound a transversely lozenge-shaped lobe, which bears a tubercle. 

 The side lobes of the tail are, like the cheeks, covered with tubercles. 



Locality. — Menevian group : St. David's. 



Agn-osttjs Bakeandei, Salter. PI. V. figs. 5 & 6. 

 Brit. Assoc. Report, 1865. 



Oval in form, highly convex, and rather less than half an inch in 

 length. Very slightly marginate, and with a smooth surface. • Gla- 

 bella rather indistinctly marked out by two faint lateral furrows, 

 less wide than the cheeks, and extending in length to about half 

 of the head. Thorax raised, axis strongly lobular, and pleura) 

 grooved. 



The axis of the tail is equal to about a third of the width. It is 

 grooved into an anterior pair of triangular lobes, into a wide middle 

 lobe, which runs across, and into a posterior triangular lobe. In the 

 groove at the base of the triangular lobe there is a rather strongly 

 raised tubercle. 



Locality. — Menevian group : St. David's. 



Aeionelltjs longicephaltjs. Hicks. PI. V. figs. 20-26. 



This species is somewhat like the Arionellus ceticephalus, Barrande, 

 and forms another important Unk in the connexion between British 

 and Bohemian primordial faunas. 



It is rather longer than the Bohemian species. The length of 

 the perfect specimen must have been rather over an inch and 

 a half; width about equal to a third of the length ; oval in form 

 and convex. Head large ; length about equal to width at base, and 

 strongly convex. Glabella conical in shape, prominent, and marked 

 by four furrows on esfch side. Eye small and remote from the gla- 

 bella, situated towards the outer margin, and rather farther back 

 than half the length of the head. The anterior facial sutures run 

 forwards in a line with the general axis — and the posterior sutures 

 backwards, to cut across the hinder margin a little to the inner side 

 of the angle, and in a line with the terminal ends of the pleuroe. 

 The axis tapers backwards ; the pleural, IG in number, are deeply 

 grooved and have blunt extremities ; the fulcrum is situated at 

 about a third of the length from the axis. The axis of the tail is 

 well raised, and composed of three annulations, the hinder one 

 being pyramidal in shape. The side lobes are grooved by furrows. 



Locality. — Menevian group : St. David's ; and near Maent^vrog, 

 l!iorth Wales. 



