92 TRILOBITES OF GIRVAN. 



the glabella. Occipital furrow distinct, marking off neck-ring of moderate width 

 ornamented with stria? arched forward. Axial furrows narrow, concave outwards, 

 diverging anteriorly. Fixed cheeks gently convex, at least half as wide as glabella, 

 and ornamented with similar arched strise. 

 Dimensions. — 



Length of glabella . . . . -}- 5 mm. 



Width „ at base . . 3 „ 



Collection. — Mrs. Gray. 

 Horizon and Locality. — Stinchar Limestone Group (Llandeilo) : Craighead. 



Genus BRONTEOPSIS, Wyville Thomson. 

 1. Bronteopsis ardmillanensis, sp. nov. Plate XIII, figs. 1 — 4. 



Specific Characters. — Head-shield short, transverse, broadly semicircular, nearly 

 three times as wide as long ; gently convex. Glabella strongly pyriform, with long 

 narrow convex neck, expanding rather suddenly into frontal lobe to twice its basal 

 width ; anterior end truncated. Pair of ill-defined small nodular lobes situated 

 at base of neck. Axial-furrows strong, deep, curving outwards anteriorly, and 

 then sharply inwards to meet in front of glabella. Small pit situated in axial furrow 

 on each side of broad anterior portion of glabella. Neck-furrow strong ; neck 

 ring rounded, with prominent median tubercle and a smaller lateral tubercle on each 

 side. Fixed cheeks convex on each side of neck of glabella, but flattened in front ; 

 half as wide again as neck. Eye-lobes placed far back, opposite basal lobes of 

 glabella ; subcircular and projecting laterally ; extending about one fourth the 

 length of the head-shield. Facial sutures with short oblique posterior branch, 

 running outwards behind eye so as to meet posterior margin of head at acute angle ; 

 anterior branch curving at first inwards and then strongly outwards, following 

 closely the outline of glabella, bending inwards in front to cut anterior margin of 

 head. Free cheeks wide, triangular; posterior and lateral edges meeting at about 45° 

 at genal angle. Inner portion of free cheek gently convex ; outer marginal portion 

 broad, flattened or slightly concave. Eyes of moderate size, about one fourth 

 the length of head, and placed very far back. Genal angles furnished with short 

 spine. Ornamentation of glabella composed of fine wavy lines parallel to its length 

 and forming loop at base of neck. 



Thorax of -\- 7 segments (seven segments are attached to one head-shield), with 

 narrow convex cylindrical axis, half as wide as the pleurae. Pleurae narrow, 

 arched downwards and slightly backwards, ending in free blunt points. Surface 

 of pleurae not well preserved, but apparently furnished with a broad median 



