﻿276 MR. F. E. C. EEED ON THE FAUNA OF [May IOIO, 



Pliomeea pseudoaeticttlata, Portl. (PI. XXII, figs. 5 & 6.) 



The head-shield of Pliomera j^eudoarticulata, Portl., has never 

 been described, and apparently no head has been found on any 

 occasion in definite connexion with the pygidium on which this 

 species was founded. There is one head-shield from the tuff (62), 

 which does not resemble that of Pl.jischeri, Eichw., or PL actinura, 

 Dalm., nor any of the British species described, but appears to be 

 more similar to PI. westoni (Billings) 1 of the Quebec Group. The 

 glabella is moderately convex, subquadrate, and subpentagonal, the 

 anterior end being strongly arched forwards and almost angulated 

 in the middle instead of truncate ; the sides are parallel, and the 

 first, second, and third pairs of lateral furrows are equidistant, 

 slightly oblique and parallel, and in length about a quarter of the 

 width of the glabella ; the posterior pair, which is rather nearer 

 the occipital furrow than it is to the second lateral furrow, is 

 slightly arched backwards ; the anterior furrows are mere elongated 

 pits at the anterior end of the glabella in front of the lateral angles, 

 are separated by about two-thirds of its width, and become very 

 weak before reaching the axial furrows. The occipital ring is not 

 well preserved, but the furrow is slightly arched forwards. The 

 axial furrows are narrow, though strong and deep. The fixed cheeks 

 are large and subtriangular with a gently convex surface, are about 

 one and a quarter times the width of the glabella, and are arched 

 down on each side. The genal angle is obtuse and rounded, and the 

 marginal and neck-furrows, which unite in a sharp curve, are of 

 uniform strength, and mark off a prominent, rounded, convex neck- 

 segment and border. The surface of the cheek is coarsely pitted ; 

 the eyes are large and situated opposite the second lateral lobes, 

 at a distance from the glabella equal to about a third of its 

 width. The anterior branch of the facial suture is not well pre- 

 served ; but the posterior branch is seen to have the typical course, 

 curving out in a sigmoidal fashion behind the eye and running 

 out almost parallel to the posterior margin of the head-shield to 

 cut the lateral edge in front of the genal angle. 



Dimensions. — Length of head-shield = 20 millimetres ;. width 

 of the same = 52 mm. ; length of glabella = 17 mm. ; width of 

 the same = 16 mm. 



Pliomera maihesii, Aug., 2 as well as the above mentioned PL 

 westoni (Billings), seems more nearly allied to this form than 

 PL jischeri or PL actinura, on account of the shape of the glabella. 

 Prom the occurrence in the Shangort Beds 3 of a precisely similar 

 type of head-shield (fig. 6), in association with an undoubted 

 pygidium of PL pseudoarticidata, we may probably refer this head- 

 shield to this species. 



1 ' Palseozoic Fossils of Canada ' vol. i (1865) p. 321 & fig. 307 a. 



2 N. P. Angelin, ' Palagontologia Scandinavica ' 1854, p. 35 & pi. xxii, fig. 1. 



3 C. I. Gardiner, S. H. Eeynolds, & F. P. 0. Peed, Quart. Journ. Geol. Soc. 

 vol. Ixv(l909)p. 125. 



