34 TRTLOBITES OF GIRVAK 



the length of the whole glabella. At the base of this spine starts another much 

 stouter longer spine which rises up vertically in the median plane and curves back 

 over two thirds of the head-shield. The posterior portion of the glabella is 

 elliptical and obscurely trilobed, being divided into three parts of subequal width by 

 two longitudinal shallow depressions in which lie two pairs of very short oblique 

 deep furrows; the anterior pair is situated just behind the front end of the eyes, 

 and the posterior pair is a little behind the middle of the eyes. Each furrow ends 

 internally in a pit. The surface of the glabella is tuberculated, but the tubercles 

 are fewer or nearly absent along the median line of the anterior portion, and in 

 the neighbourhood of the longitudinal depressions. Eye-lobes about one third the 

 length of the glabella and embracing posterior portion, narrow, smooth, semi- 

 annular, depressed, separated from glabella by deep furrow. Occipital furrow 

 straight and strong. Occipital ring of uniform width, extending on each side 

 beyond the longitudinal depressions on the glabella, ornamented like glabella, but 

 with one large median tubercle. Free cheeks angulated posteriorly, the posterior 

 margin meeting the lateral at nearly a right angle, and the genal spine not arising 

 at this point but about halfway up the lateral margin. Genal spines long, 

 flattened, pointed, two or three times the length of the eyes, gradually tapering, 

 curved slightly outwards and backwards, marked with oblique longitudinal 

 striations on under surface. Surface of free cheek swollen into convex rounded 

 ridge, tuberculated like glabella, and running in front of and outside but not 

 behind eye. Narrow rounded border to free cheek marked off by deep marginal 

 groove. Eyes large, semi-annular, convex, elevated, with narrow rim at base 

 encircled by broad shallow groove separating it from free cheek. Surface of eye 

 furnished with numerous minute lenses arranged in diagonal rows. 



Thorax with -\-9 (P 11) segments; axis convex, cylindrical, very slowly tapering, 

 wider than pleurae. Axial rings ornamented with three or four irregular rows of 

 tubercles ; posterior margin serrated ; anterior margin furnished with rounded 

 articulating crescentic band. Pleura? falcate, weakly recurved, scarcely bent 

 down, two thirds the width of axis; surface excavated; fulcrum about halfway 

 out, weak, marked by elevation of anterior margin instead of by projecting knob 

 as usual in Remopleurides. Extra-fulcral portion very slightly recurved, grooved, 

 ending in point ; posterior margin not distinctly notched. 



Pygidium small, with short broad convex triangular axis of three segments, 

 not reaching posterior margin ; anterior ring only complete, the two posterior ones 

 being confluent on each side but separated in centre by short strong furrow not 

 reaching axial furrows. Pleural portions narrow, of two pairs of pleura?. First 

 pair broader than second, with very approximate fulcrum and beyond it bent back 

 subparallel, terminating in rather long free points extending behind those of the 

 second pair. Second pair of pleurae narrow, short, touching in middle line behind 

 axis, with short obtuse free points. 



