20 TRILOBITES OF GIRVAN. 



four times as long as wide, extending tliree-fourtlis the length of glabella, steeply 

 inclined on each side. No meso-occipital ring present. 



Thorax of five segments ; axis convex, sub-cylindrical, tapering very slightly 

 posteriorly ; rings ornamented by a few fine strige. Pleurae short, broad, arched 

 down at fulcrum at about one-third their length ; inner portion crossed by broad 

 shallow pleural groove behind raised anterior margin ; outer portion smooth, with 

 triangular articulating facet ; fine post-median impressed line along whole pleura 

 parallel to posterior edge ; extremities of pleurae abruptly truncate, obtuse. 



Pygidium semi-oval, nearly as long as wide, strongly and uniformly convex, 

 smooth, sub-hemispherical, with no trace of axis except faint notches on anterior 

 margin ; slightly thickened narrow border marked off by very weak marginal furrow. 

 Dimensions. — 



Length of trilobite .... 17*00 mm. 



,, of head .... 8'50 „ 



,, of thorax .... 3'50 „ 



,, of pygidium .... 5"00 ,, 



Width of head .... 9-00 „ 



,, of glabella at base . . . 4'25 ,, 



,, of thoracic axis posteriorly . . 3*25 ,, 



" of pygidium .... 8*00 „ 



Remarks. — There is only one specimen of this species in Mrs. Gray's collection, 

 and on it the above description is based. The glabella and eyes recall C. mirahilis 

 (Forbes)^ but the apparent lateral expansion of the glabella in front of the eyes is 

 peculiar, though this part of the head is not quite satisfactorily preserved. The 

 thorax is much like that of G. major (Salter)^, but the pygidium resembles that of 

 C. boia (Hicks)^ from the Arenig beds of St. Davids; and the young individuals of 

 C. speciosa, Corda, figured by Barrande,* have also an unfurrowed smooth 

 pygidium. 



Horizon and Locality. — Whitehouse Group (M. Bala) ; Shalloch Mill. 



Cyclopyge subarmata, sp. nov. Plate III, figs. 9 — 12. 



1904. Cyclopyge armata (Barraude) Eeed, op. cit., pt. ii, p. 51, pi. vii, figs. 11 — 14; pi. viii, fig. 1. 



Specific Characters. — Head-shield nearly as long as thorax and pygidium 

 combined. 



Glabella suboval, egg-shaped, narrowing anteriorly and produced into short, 

 triangular, frontal spine ; surface of glabella very gently convex, marked by two 

 pairs of short transverse furrows, horizontal or slightl}^ arched, isolated from axial 



1 Salter, ' Mem. Geol. Surv.,' dec. vii, pi. x, figs. 8, 8 a. 



" Salter, ibid., pi. x, figs. 9, 9 a, 9 b. 



3 Hicks, ' Quart. Journ. Geol. Soc.,' vol. xxxi (1875), p. 185, i>\. x, figs. 9, 9 a. 



* Barrande, ' Syst. Silur. Boheme,' vol. i, Suppl., p. 64, [A. ii, figs. 17—18. 



