BRACHYMETOPUS. 49 



the head produced into short, slightly recurved spines ; entire surface of head 

 covered with small bead-like tubercles, five larger ones being placed around the 

 front border of the glabella and one in advance of each eye on the free-cheeks. 



Thorax not known. 



Pygidium circular, one fourth wider than long, consisting of seventeen coalesced 

 somites, the axis forming one third the entire breadth of the shield where it joins 

 the thorax, but diminishing rapidly to a rather blunt extremity at about one fifth 

 of its length from the margin of the tail-shield which encircles it ; each ring of the 

 axis ornamented by a row of small granular tubercles (somewhat irregular in size) ; 

 about eight grooved pleurae are seen on each side the axis, each pleura forming a 

 raised rib, extending to and becoming wider at its rounded extremity near the 

 border, marked by a row of small tubercles, and having a shorter intermediate rib, 

 similarly ornamented, placed behind it in the furrow ; the pleuras, as well as the 

 axis of the pygidium, are convex ; the margin has a slight narrow rim around it. 



Formation. — Carboniferous Limestone. 



Locality. — Settle, Yorkshire; Caldbeck, Cumberland; Castleton, Derbyshire ; 

 Little Island and Blackrock, Cork ; Ardshanbally, Limerick. 



Many specimens of this species have been examined from the British Museum 

 (Natural History), the Woodwardian Museum, Cambridge, the Museum of the 

 Geological Survey of Ireland, and from the collections of the Rev. B. 0. de la Hey, 

 Cheshire, and Mr. Joseph Wright, F.G.S., of Belfast. 



Subjoined is de Vernueil's original description of a pjrgidium of a Trilobite 

 from the Carboniferous Limestone of Cosatchi-Datchi, East of the Urals (' Greol. 

 Russia ' (vol. ii, Palaeontology, p. 378, tab. 27, fig. 16 a, b), and named by him 

 Phillipsia ouralica (1845). 



" Abdomen semielliptical in form and arched, median lobe produced, narrow, 

 subtriangular, and composed of fourteen articulations of which only ten are visible, 

 the four last being very small and compressed. The lateral lobes are larger than 

 the median lobe, and surrounded by a straight granulated border. The nine pleurso 

 composing the tail are divided by a groove into two unequal parts, the narrower 

 being ornamented by fine granulations, whilst the larger half bears tubercles twice 

 as large. The median lobe is not prolonged to the posterior border, but is separated 

 by a smooth and rounded border which divides the two series of lateral pleura?. 



" Dimensions. — Length 10 millimetres, breadth 12 mm. The breadth would be 

 more considerable if the form of the abdomen was less arched. Median lobe 4 

 mm., lateral lobe 5 mm. 



"Affinities and differences. — By the subdivisions of the lateral articulations, this 

 species, of which the abdomen only is known, is easily recognised. It cannot be 

 considered equivalent to P. Jonesii, of Portlock, although it has much resemblance. 

 Nevertheless, if we consult De Koninck's figure of this species we see that it differs 



