Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/216

 shape, and divided about its anterior third by 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 of somewhat triangular 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.

Agnostus Barrandei, Salter. Pl. 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. Glabella 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 pleurae 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.

Arionellus longicephalus. Hicks. Pl. V. figs. 20-26.

This species is somewhat like the Arionellus ceticephalus, Barrande, and forms another important link 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 each side. Eye small and remote from the glabella, 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 pleurae. The axis tapers backwards ; the pleural, 16 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 Maentwrog, North Wales.