Crustacea. | LOWER PALAZOZOIC ARTICULATA. 145 
T. elongatus (Port.) t. 1. B. fig. 7 only differs in the entire animal being longer and narrower, the length 
of the cephalic shield being considerably more than half the width—One specimen of this variety has occurred 
in the schists of Pwllheli. 
TRINUCLEUS GIBBIFRONS (J/°Coy). Pl. 1. E. fig. 14. 
Ref.—M Coy, Ann. Nat. Hist. 2nd Series, Vol. [V 
Sp. Ch.—Cephalic shield nearly semicircular, length rather more than one-third of the width; glabella 
pyriform, rounded in front, gradually narrowing towards the base, compressed, exceedingly gibbous, its 
height above the cheeks nearly equalling its width; on each side of the neck-furrow (in casts) there is 
a deep puncture, and another similar a little in front of it; a small spine on the neck-furrow; cheeks 
spherical triangles, height and width about equal, moderately convex; border of moderate width, three 
rows of punctures in front of the glabella and four rows in front of the cheeks, more numerous at the 
sides, generally connected in front by radiating furrows, forming an imperfect fimbriation. Usual length 
of cephalie shield three lines. Surface very minutely granulated. 
This very common species is figured without a name by Portlock (Geol. Rep. Pl. 1. B. fig. 13 and 14), 
The fine granulation of the lobes of the head, and the extreme prominence of the gradually narrowing, pyri- 
form, compressed glabella separate this at once from either the 7. Caractaci or T. latus, with which it 
seems to have been confounded; it is wider than the former, less so than the latter. From the two little 
punctures on each side of the base of the glabella this strongly approximates to the 7’. scyllarus (His), as 
distinguished from 7. seticornis, but, although with abundance of specimens, I cannot find any trace of 
ocular tubercles or eye-lines in the midst of the cheeks, as in Tretaspis, to which those species belong ; 
these punctures indicate, no doubt, the insertion of the muscles of the jaws, but are not extended into 
transverse segmental furrows as in those last-named species; in the radiation of the border and number 
of rows of pores in front, it approaches slightly to the 7. radiatus (Murch.), but is distinguished by the 
head being rounded, the cheeks wider, and the border not being more than half the depth as well as 
being by no means so distinctly radiated. 
Position and Locality—Common in the limestone of Goldengrove, Llandeilo; the schists of Tre Gil, 
S. of Llandeilo; and Alt yr Anker, Meifod, Montgomeryshire ; also at Pen y Craig, above Llangynyw, 
Montgomeryshire; a variety with a shorter shield, the lobes of which are more spherical, perhaps from 
pressure, occurs in the black shale three miles N. of Builth, Radnorshire. 
Explanation of Figqures.—Plate 1, E. fig. 14. Natural size, Caradoc sandstone, Goldengrove.—Fig. 14a, 
Ditto, magnified three diameters. 
Trinuc.tevus Latus (Porth). Pl. 1. E. fig. 15. 
Ref.—Portk. Geol. Rep. Pl. 1. B. fig. 11 and 12. 
Sp. Ch.—Cephalic shield smooth, transversely elongate, from three to four times wider than long ; 
anterior and posterior margins subparallel, the angles produced laterally (not deflected backwards) ; glabella 
convex, with nearly parallel sides, anterior and posterior ends almost equal, obtusely rounded; cheeks 
transversely semielliptical, about one-third wider than high, gently convex. Average length of cephalic 
shield four lines. 
Confounded with the 7. jimbriatus by Portlock, from which it differs in the margin, being punctured, 
not radiated, the posterior half of the glabella not being contracted nor furrowed at the sides, and the 
lobes of the shield being smooth and the cheeks destitute of the ocular tubercles, or eye-line. 
Position and Locality.—Rare in the schists at Selottyn Road; Gelli Grin, Bala, Merionethshire ; 
Maes Meillion, S. of Bala, Merionethshire; Llwyn y Ci, N.W. of Bala; Bryn Evan Yspatty; Rhiwlas, 
N. of Bala; Pen Cerrig Serth. 
Explanation of Figure—Plate 1. E. fig. 15. Specimen natural size from Tyrone, shewing antennary 
pores, and general transverse form. 
U 
