There is one complete individual of a species of Phacops from the Orthis-argentea zone of Prendergast Lane, Haverfordwest, showing certain interesting characters which make it worthy of notice. The head is somewhat crushed and imperfect, but the glabella is seen to be large and broad and to expand regularly towards the front; the frontal lobe is transversely rhomboidal and nearly half the total length of the glabella; there are three pairs of lateral lobes, of which the anterior pair is the largest; the second pair is narrower, and the third pair is subequal to the second in size. The first pair of lateral furrows is oblique; the second pair is horizontal and slightly arched forwards; the third pair is slightly oblique and the most strongly marked of all; the occipital furrow is strong and curved forwards in the middle. There is only a narrow median strip of the glabella not crossed by the lateral furrows, for they are rather long and all reach inwards to about the same extent.

The thorax has a prominent axis about three-fourths the width of the pleuræ, which are bent downwards and backwards beyond the fulcrum, which is situated at about half their length. Their extremities are slightly bent forwards and apparently rounded or bluntly pointed; a deep diagonal furrow traverses the whole length of each pleura.

The pygidium is nearly semicircular, with a regular rounded margin, except behind the axis, where there is developed a long, pointed, straight posterior spine, about two-thirds the length of the pygidium.