88 BRITISH CAMBRIAN TRILOBITES. 



is very narrow, running close to the anterior ridge, becoming somewhat broader 

 towards its extremity, where it bends back and is continued into the point; the 

 pleurae end in short re-curved points. 



The very narrow axis and wide pleurae at once distinguish this species from 

 any other except Ct. pecten. In that species the pleurae are more slender and there 

 is no indication of the raised ridges along the borders. 



The species is referred by Salter to Olenus (Sphserophthalmus) and by Reed to 

 Olenus (Ctenopyge ?). Mr. Reed remarks that " it is extremely doubtful to what 

 subgenus or even genus this imperfect fossil should be ascribed. It however 

 seems more allied to Eurycare or Ctenopyge than to Sphderophthalmus." In spite 

 of the peculiarity of the pleurae, they are certainly more like those of 67. pecten 

 than those of any other trilobite with which -I am acquainted, and I agree, therefore, 

 with Mr. Reed in referring the species to Ctenopyge. 



Horizon and Locality. — Upper Lingula Flags: Moel (Iron. 



6. Ctenopyge teretifrons (Angelin). Plate X, figs. 9, 10. 



1854. Sphserophthalmus teretifrons, Angelin, Pal. Scaud., p. 49, pi. xxvi, fig. 10. 



1880. Ctenopyge teretifrons, Linnarssou, G-eol. Foren. Stock. Forh., vol. v, p. 152, pi. vi, figs. 12, 13. 



Head very strongly emarginate in front. Glabella narrow, long, reaching the 

 marginal furrow, the front portion somewhat expanded, swollen and rounded. One 

 pair of glabellar furrows, oblique, probably meeting across the middle line, but 

 there very shallow ; neck-furrow also shallow towards the middle, neck-segment 

 with a median tubercle. Eyes placed rather far forwards and at a distance from the 

 glabella almost twice the width of the latter ; ocular ridge almost at right angles to 

 the axis. Facial suture cutting the anterior margin considerably to one side of the 

 glabella, running in nearly a straight line from the anterior margin backwards and 

 outwards to the eye, behind the eye curving backwards and only slightly out- 

 wards to the posterior margin. Fixed cheeks at the eye almost twice the width 

 of the glabella, somewhat convex, not much expanded behind the eye; posterior 

 margin sigmoid, curving forwards towards its outer extremity. 



Dimensions. — Cranidium about 2 mm. long in the axial line, 5 - -l mm. wide at 

 the posterior margin (measurements taken from the uncompressed specimen, Plate 

 X, fig. 10). 



Although the specimens here described are far from perfect, their resemblance 

 to Angelin's type as figured by Linnarssou is so close that there can be little doubt 

 that they belong to the same species. The ocular ridge does not show quite the 

 same curvature, and the small tubercle on the front lobe of the glabella is not visible 



