Contributions to 'Palaeontology. 



123 



upper side : frontal limb convex, a little wider in the 

 middle than at the sides, separated from the glabella by 

 a wide slightly curving furrow. 



Movable cheek subtriangular, with a wide deep ocular 

 sinus at the inner angle, convex towards the eye, with 

 a wide shallow depression just within a broad elevated 

 limb ; posterior margin short, the genal angle produced 

 in a long nearly straight spine, which is more than 

 twice as long as the body of the cheek. 



Hypostoma subelliptical, with a slight angular extension 

 on each side a little behind the centre ; border elevated 

 along the sides, and slightly truncate in front : an ob- 

 lique depression on each side near the anterior end, 

 directed from the margin forward and towards the 

 middle. 



Axis of the thorax convex and strongly defined : lateral 

 lobes wider than the axis, except at the posterior part, 

 where they are nearly equal. 



Pygidium somewhat semielliptical, wider than long, round- 

 ed in front : axis strong and highly elevated, conical, 

 tapering somewhat rapidly, marked by five annulations 

 besides the elongated posterior one and the anterior 

 articulating segment. Lateral lobes convex near the 

 axis, and at the middle of their width sloping abruptly 

 downwards, with a flattened continuous margin; marked 

 by four distinct ribs which are deeply divided through- 

 out their length, and become merged in the flattened 

 limb : the anterior simple rib is prominent, subangular, 

 and continued to the margin of the border. The con- 

 tour of the margin is apparently continuous and unin- 

 terrupted by spiniform extensions. 



This species is readily distinguished from the preceding, by the 

 narrow frontal limb of the glabella; in the cheeks, by the long 

 spine ; and in the pygidium, by the more prominent axis and less 

 expanded border, without the posterior spiniform extensions. 



