10 TRILOBITBS OF GIRVAN. 



Harpes (Eoharpes) hornei, sp. nov. Plate II, figs. 1, 2. 



Specific Characters. — Shape oval; width nearly three-fourths the length. 

 Head-shield large, sub-oval, with elongated limb ; horns of limb produced back 

 so as to embrace whole thorax and pygidium and nearly to touch each other 

 behind it. Head-shield proper (apart from limb) serai-oval, strongly convex, rising 

 suddenly and steeply on all sides from limb. Glabella subconical, convex, pro- 

 minent, subcarinate, about one-third the width and nearly three-fourths the length 

 of the head-shield, narrowing anteriorly ; with a pair of triangular basal lobes 

 marked off by oblique furrows arising at rather less than one-third the length of the 

 glabella from base and meeting the occipital furrow behind at about one-third the 

 width of the glabella on each side. Axial furrows not deeply impressed, almost 

 obsolete in front of glabella. On each side of anterior half of glabella the cheeks 

 rise into large low conical bosses, each of which bears two separate ocelli. Behind 

 these bosses and adjoining glabella are flattened, smooth semicircular areas 

 (al?e), each marked out by a strong, curved furrow arising at right angles from the 

 axial furrows at the same level as the lateral furrows of the glabella, and sweeping 

 round to unite with the meso-occipital furrow at the base of the glabella ; each ala 

 is longitudinally divided into two subequal, crescentic portions by a shallow gently 

 curved groove. Meso-occipital furrow weak in middle, but strongly impressed 

 behind basal lobes of glabella. Meso-occipital ring convex, of moderate width, 

 simple. Pleuro-occipital segment narrow, prominent, elevated. Upper slopes of 

 cheeks and eye-bosses covered with sparsely distributed minute pits, tending to a 

 radial arrangement on the bosses. Lower half of cheeks (cheek-roll) and of pre- 

 glabellar area separated from upper half by narrow continuous groove (lateral line) 

 and in front of glabella by line of larger pits, and possessing slight independent 

 convexity ; surface of pre-glabellar area and cheek-roll coarsely pitted. At the 

 genal angles the cheek-roll is produced posteriorly into elongated, tapering, 

 steeply inclined prolongations reaching back as far as pygidium, closely appressed 

 against ends of pleurse, united along lower edge with inner margin of limb nearly 

 at right angles and marked with line of larger pits. 



Limb flat, horizontally extended, of nearly uniform width all round head-shield 

 (i. e. about one-half the length of the head-shield) ; behind head-shield limb decreases 

 in width very gradually and is prolonged into slowly tapering horns curving 

 gently inwards and embracing whole thorax and pygidium, so that their pointed 

 extremities are less than the width of the head-shield apart. 



Surface of limb covered with coarse pits similar to those on cheek-roll, quite 

 irregularly distributed, with minute puncta3 between them ; near the outer and 

 inner edges of the limb the pits are somewhat larger, and a rather irregular ro^v 

 of still larger ones runs round the inner and outer margins. Border very narrow. 



