52 TRILOBITES OF GIRVAN. 



nevertheless, there are a few points of difference which seem to warrant its specific 

 separation. The head-shield in our Girvan form is less transversely expanded, the 

 first lateral lobes are larger, the thoracic axis does not increase in width behind the 

 head, the fulcrum on the pleuree is not so far out, and there is no strong node at 

 the base of the pleurae ; the double line of tubercles on the pleurae of the p3'gidium 

 is very much fainter. 



The Russian species PIi. l-ncl-ersianus, Schmidt,^ and PJi. iiieszhoirdii, Schmidt,- 

 are also allied to Ph.. refiirdntux in general cephalic characters. 



Horizon and, Locallfij. — Starfish Bed, Drummuck Group (U. Bala) : Thraive Glen. 



Phacops (Pterygometopus) huiiteri, sp. no v. Plate VIII, figs. 8, 0. 



Specific Gharacters. — Head-shield transversely semicircular, genal angles 

 unknown. Glabella subclavate, rounded, gently convex ; frontal lobe transverse, 

 about half the length of glabella, anteriorly rounded, twice as wide as long, with 

 lateral angles not projecting ; first lateral lobes large, triangular, extending about 

 one-third along side of glabella, and about one-third across it on each side ; second 

 lateral lobes small, oblong, not reaching axial furrows, parallel sided, not tubercular ; 

 basal lateral lobes larger than second lateral lobes, expanded at outer ends into 

 large tubercules, extending forwards so as nearly to touch first lateral lobes on 

 axial furrows. 



First lateral furrows straight or slightly curved, obliquely directed backwards 

 at about 45° to axial furrows ; second lateral furrows shorter, straight, directed 

 slightly forwards at about 90° to course of axial furrows ; third lateral furrows 

 short, obsolescent, not reaching axial furrow, parallel to second lateral furrows. 

 Meso-occipital segment rounded, wider than basal lobes, marked off from glabella 

 by strong arched furrow ; Avitli small rounded lateral nodules, projecting at sides. 

 Surface of glabella coarsely tuberculated. 



Eyes large, reaching from lateral angles of frontal lobe to neck-furrow, arched 

 outwards, meeting pleuro-occipital segment nearly at right angles, and enclosing 

 swollen portion of cheek fully two-thirds the basal width of glabella. Eye-lobe 

 broad, smooth, upturned, separated from cheek and extending whole length of eye. 

 Surface of cheek coarsely tuberculated. 



Thorax with broad cylindrical axis, as wide or rather wider than pleural lobes ; 

 axial rings with well-marked lateral nodular swellings ; i)leurjB short, with obtuse 

 ends, and traversed by deep diagonal pleural furrow. 



Pygidium unknown. 



1 Schmidt, ' Eev. Ostbalt. 8ilur. Trilob.," pt. i (1881), p. i>0, pi. v, tigs. 11—13. 



2 Schmidt, ibid., p. 92, pi. v, iigs. 14, 15. 



