Carboniferous Limestone Trilobites. 449 
acute angle, where it joins the glabella in front and a less acute 
angle behind the eye, where it unites with the posterior border. 
A broad groove or furrow surrounds the free cheek, running exactly 
parallel to its own outer border: the posterior angles of the head 
project slightly backwards, but are not produced into cheek-spines. 
The incurved under margin of the shield is finely striated as well as 
punctated. The hypostome (seen in sité in one of our specimens) 
is large, the mesial lobe is broad and spatulate, the surface being 
finely striated with wavy longitudinal lines; the lateral lobes or 
alee are small, smooth, and pointed. 
The thorax, which is roundly arched, consists of nine smooth and 
well-defined segments, the first only having a minute tubercle on 
the centre. The axis of the thorax, which next the head is con- 
siderably broader than its side lobes, diminishes gradually in breadth 
backwards to the pygidium, where it is only equal to its pleure in 
breadth; the pleuree, which are smooth, are all faceted to enable 
the animal to roll itself up into a ball. The axis of the abdomen, 
or pygidium, shows it to be composed of thirteen coalesced segments, 
the pleuree being united in a rounded shield, the border of which is 
smooth, as the ribs die out before they quite reach the margin. 
There is a faint tendency to ornamentation on the axis of the tail. 
Formation.—IJn Carboniferous Limestone and in “ Rotten-stone ” 
band. 
Localities.—Bolland and Settle, Yorkshire ; Castleton, Derbyshire; 
“Rotten Stone,” Matlock, Derbyshire; Longnor; Arnside; Black- 
rock and Little Island, Co. Cork; Middleton; Carnteel, Tyrone; 
Castlepollard, West Meath, and Limerick, West of Dromore Wood. 
Specimens of P. Derbiensis have been examined from the National 
Collection, British Museum (Nat. Hist.), Cromwell Road; the Museum 
of Practical Geology, Jermyn Street; the Woodwardian Museum, 
Cambridge ; the Museum of the Geol. Survey, Dublin; and from 
the collections of the Rev. EH. O. de la Hey, M.A., Marple, Cheshire, 
and Joseph Wright, Esq., F.G.S., Belfast. 
Puiniresta Coner, M‘Coy, 1844. Plate XJ. Fig. 2. 
Phiilipsia Colei, M‘Coy. 1844. Synop. Carb. Foss. of Ireland, 4to0. p. 161, tab. 
iv. fig. 6. 
Morris. 1854. Cat. Brit, Foss. 8vo. p- 114. 
H. Woodw. 1877. Cat. Brit. Foss. Crust. p. 55. 
ee HVoodwa 18835) Balk) Soc) Mon. Carb: Irilob. part 1 ps 165 
pl. u. figs. 1-10. 
Head-shield broadly semicircular; glabella but slightly elevated, 
the central convexity not reaching to the front border, but separated 
by a broadly-expanded margin which makes the head one-third 
wider in front than at its posterior border; glabella marked by two 
short lateral furrows, and by a small basal lobe on each side, the 
neck-furrow is rather strongly marked, the neck-lobe is slightly 
broader than the first free segment; the posterior margin is divided 
obliquely by the facial suture, which runs in a very undulating line 
between the glabella and the free-cheek ; eyes large, reniform, no 
facets visible ; cheeks arched, somewhat produced at the posterior 
DECADE II.—VOL. X.—NO. X. 29 
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