LICHAS (AMPHILICHAS) HIBERNICUS. 107 



than twice its basal width ; anterior outline arched; anterior lateral angles pointed 

 at about 45° and overhanging inner half of lateral lobes ; posterior half of median 

 lobe with nearly parallel sides and less convex. First lateral furrows strong, deep, 

 curving strongly inwards at first to about middle of median lobe, thence running 

 back almost parallel and straight to meet occipital furrow at right angles. 

 Lateral lobes tricomposite, suboval, elongate, more than twice as long as wide, 

 pointed in front, truncated obliquely behind, gently convex, less elevated than 

 median lobe ; of nearly uniform width for more than two thirds of their length, 

 then rapidly narrowing to pointed anterior extremity ; extending about four fifths 

 the length of the glabella, and of less width than median lobe at base ; strongly 

 bent down with general curvature of head-shield at about half their length. Axial 

 furrows deep, equal in strength to first lateral furrows, strongly curved, nearly 

 parallel to axial furrows, concave outwards as far as front end of lateral lobes, round 

 which they bend inwards to meet first lateral furrows at anterior lateral angles of 

 glabella, and pass into marginal furrow. Marginal furrow marking off very narrow 

 rounded border on anterior margin in front of glabella. 



Occipital furrow straight and horizontal behind median lobe, and at right 

 angles to first lateral furrows, outside of which it is directed obliquely backwards 

 behind lateral lobes. Occipital ring broadest behind median lobe, where it is of 

 uniform width, but behind lateral lobes it decreases in width. Occipital lobes 

 completely absent. 



Fixed cheeks with narrow band-like flattened anterior wing alongside lateral 

 lobes ; posterior wing broad, triangular, gently convex. Neck-segment widening 

 laterally, marked off by strong furrow. Facial suture cutting anterior margin just 

 above lateral angles of glabella, thence curving outwards back to eye-lobe which it 

 encircles, behind which it runs outwards and backwards in a weakly sigmoidal 

 curve to cut posterior margin at about 60° at a distance from the axial furrow 

 equal to about one third the width of the glabella. Eye-lobe situated opposite 

 middle of lateral lobe where the downward curvature commences ; of moderate size, 

 rounded, semicircular, with eye-furrow near base. Surface of glabella, occipital 

 ring and cheeks covered with closely-set low round hollow tubercles varying some- 

 what in size and prominence. 



Remarks. — There has never been any adequate description of the head-shield 

 called L. hibernicus, Portlock's original account being insufficient, and that given by 

 Nicholson and Etheridge (op. cit.) being scarcely full enough for all purposes. 

 The above description, therefore, based on the specimens used by Portlock and on 

 other examples from the typical locality, Kildare, may be advantageous. The Girvan 

 specimens agree with this diagnosis of L. hibernicus in all particulars so far 

 as they are preserved. Schmidt 1 was of the opinion that his L. holmi was prob- 

 ably identical, but of this I cannot feel certain. 



1 Schmidt, ' Rev. Ostbalt. Silur. Trilob.,' pt. ii (1885), p. 54, pi. vi, figs 1-4 — 17. 



