288 ME. E. S. COBBOLJ) ON TEILOBITES L^Ug- I 9 1 I > 



I dedicate this species to Mr. Philip Lake, who has so frequently- 

 befriended me in my study of the Comley trilobites, and who first 

 pointed out to me the reference of these fossils to Dames's genus. 



Cranidium : General form. — Irregularly pentagonal, with the 

 anterior border rounded in front of the glabella, but nearly straight 

 in its continuation towards the sides. 



Size. — Moderate ; length of the type-specimens = about 8 milli- 

 metres, exclusive of the spine ; width, across the eye-lobes = about 

 10 mm., across the posterior angles = about 11 mm. Other specimens 

 indicate lengths varying from 21 to 20 mm., exclusive of the spine. 1 



General convexity. — Very strongly marked, about 1:2.4 2 in 

 the type-specimens, about 1 : 3 in others. 



Glabella. — Strongly convex, both transversely and longi- 

 tudinally; distinct from the occipital ring; about five-sixths of 

 the total length of the shield, exclusive of the spine ; the sides are 

 nearly straight, and converge more or less rapidly backwards ; the 

 width of the most convergent glabella at the anterior third is 

 about three-quarters of the length of the glabella, while at the 

 posterior end it is not much more than half that length : there is 

 no trace of any furrow to be seen, unless it be the little pit on the 

 line of the axial furrow, and a modification of the surface-markings, 

 mentioned below. 



Occipital furrow. — Well defined; rather narrow, and fairly 

 uniform, in both width and depth, throughout ; very straight in 

 its course, but, when viewed from above, it appears to be slightly 

 curved backwards by reason of the convexity of the glabella. 



Occipital ring.— Of equal width with the base of the glabella ; 

 slightly broader in the middle than at the sides ; armed with a 

 short, sharp, and slightly curved spine, which rises from the 

 posterior half of the ring, and is directed upwards and backwards ; 

 the ring is arched upwards very strongly as viewed from behind, 

 and must have accommodated a very convex thoracic axis. 



Axial furrow. — The glabella is very distinctly outlined by 

 the change of curvature all round, but the furrow is scarcely at all 

 impressed, except near the anterior ends of the sides of the glabella, 

 where it sinks to a very distinct pit, which is impressed from the 

 side rather than vertically downwards, and may represent one d¥ 

 the glabellar furrows (see PI. XXV, figs. 1 & 5). 



Fixed cheeks. — Triangular in the view from above ; convex; 

 nearly horizontal close to the glabella, but curving down rapidly 

 to the eye-lobe and also both forwards and backwards. 



Eye- lobe. — Small, about a sixth of the total length of the 

 head-shield ; at a low level as compared with the cheek, from 

 which it projects horizontally ; not raised at the edge ; situated 

 about midway in the length of the cranidium. 



Ocular ridge. — Obsolete. 



1 The size of the largest head-shield collected points to a total length, in the 

 complete trilobite, of 60 to 70 millimetres. 



2 These numerals represent the proportion of the height of the shield to its 

 width. 



