PROETUS PROCERUS. 77 



3. Proetus procerus, Nicholson and Etheridge, 1879. Plate XI, figs. 5, 0, 6 a. 



1879. Proetus procerus, Nicholson and Etheridge, Mon. Silur. Foss. Grirvan., fasc. ii, p. 174, pi. xii, 



fig. 11. 

 1899. Proetus procerus, Mem. Geol. Snrv., Silur. Rocks Brit., vol. i, Scotland, pp. 524, G73, 689. 



Specific Characters. — General shape elongate oval, twice as long as wide. 



Head-shield parabolic, length rather more than two thirds the width, gently 

 convex, bent down at sides, surrounded by narrow rounded border separated off 

 by well-marked marginal furrow. Glabella convex, oblong, narrowing a little 

 anteriorly, rounded in front, rather longer than wide, very slightly contracted 

 between eyes. Lateral furrows indistinguishable, except a faint trace of a pair of 

 oblique basal farrows starting at sides opposite middle of eyes and marking off 

 triangular basal lobes. Glabella separated from anterior border by narrow raised 

 pre-glabellar band uniting fixed cheeks. Axial furrows narrow, deep, uniting 

 in front of glabella, and converging slightly anteriorly. Occipital furrow strong, 

 deep, arched forwards at sides and in middle; occipital ring rather broad; occipital 

 lobes obsolete. Fixed cheeks very narrow, but widening in front of eyes. 

 Palpebral lobes of moderate size, situated by their own length from posterior 

 margin of head-shield, and extending along middle of glabella for about one third 

 of its length. Facial sutures curving strongly outwards in front of eyes to cut 

 anterior margin; posterior branches bending outwards to cut posterior edge at about 

 45° below eyes. Free cheeks triangular, with strong neck furrow cutting off neck 

 segment, and genal angles furnished with short spines extending to third thoracic 

 segment, and longitudinally striated beneath. Eyes close to glabella, opposite 

 its middle and extending about one third of its length ; crescentic, elevated, 

 with convex surface, and wide shallow groove surrounding their base. 



Thorax of ten segments. Axis convex, cylindrical, gently tapering, wider than 

 pleurae. Axial furrows strong. Pleura? with their distal half curved sharply 

 downwards ; wide strong diagonal pleural groove on surface ; extremities rounded. 



Pygidium semicircular. Axis conical, rounded, convex, strongly elevated, of 

 5 — G segments, about one third the width of pygidium and nearly reaching 

 posterior margin, with which it is connected by short low pointed terminal 

 appendage. Lateral lobes gently convex and bent down, with 3 — 4 faint pleurae 

 visible. (A narrow border surrounds the pygidium in the type specimen, which is 

 a cast.) 



Dimensions. — 



Length of body .... 14*0 mm. 



,, of head .... 5*5 „ 



Width of „ . . . 7-5 „ 



