﻿Vol. 66.] THE CAMBRIAN ROCKS OP COMLEY. 25 



Occipital ring.— Equal in width to the glabella ; bearing (the 

 base of) a strong spine or large tubercle [401] (PL III, fig. 7). 



Axial furrow. — Very deep and wide. 



Fixed cheeks. — Anterior limit marked by a curve of rather 

 long radius, convex forwards and passing just clear of the apex of 

 the glabella. In transverse section the cheeks rise steeply out of 

 the axial furrows, then become horizontal, and finally rise to the 

 rather wide and elevated eye-lobe (PI. Ill, figs, o & 6) ; the posterior 

 angle is much depressed ; the posterior margin of each cheek is 

 furnished with two curious little circular mounds [401, 402] 

 {PI. Ill, figs. 5,6& 8). 



Ocular ridge. — Well defined on the internal cast (PL III, 

 fig. 7) ; arising on the outer side of the axial furrow a little below 

 the apex of the glabella, and passing almost directly across the 

 •cheek to the eye-lobe ; not always visible on the exterior. 



Eye -lobe. — About a third of the length of the glabella, and 

 situated far out and rather forward ; the anterior end of the eye -lobe 

 is distinctly higher than the posterior. 



Posterior margin. — Unknown. 



Frontal limb. — Swollen up to a great height in the middle, as 

 high as, or higher than, the maximum elevation of the glabella, from 

 which it is separated by a deep hollow ; the prominence decreases 

 in width and falls away in height to right and left, but continues to 

 be well marked and is separated from the cheeks by the continua- 

 tion of the deep hollow already mentioned. 



Facial suture. — Somewhat doubtful ; anterior branch (PL III, 

 fig. 6) short and direct to the margin ; posterior branch, so far as can 

 be made out from the specimen (fig. 5), taking a sigmoidal curve 

 •outwards to cut the posterior margin in line with the outer edge of 

 the eye-lobe. 



Test. — Finely granular, as seen under a strong lens. 



The prominent front and elevated eye-lobes, together with the 

 •depressed apex of the glabella, suggested when first seen the coiffure 

 of a clown, hence the proposed specific name. A restoration of the 

 complete cranidium, based upon the three specimens figured, is given 

 in PL HI, fig. 8. 



Locality and horizon. — The Olenellus Limestone of Coniley, 

 from the excavation 200 yards south of the quarry. 



This species is very closely allied to the Siberian form Ptychoparia 

 ■czekanowskii, von Toll. 1 It differs (i) in the shape of the glabella; 

 (ii) in the front outline of the cranidium ; (iii) in the strength of the 

 nuchal spine, which in the Siberian species is described as entirely 

 replacing the occipital ring. In E. von Toll's figures there is an 

 uncertain indication of an upturned marginal rim, in advance of 

 the swollen frontal limb ; no trace of this is to be detected in the 

 €omley form. 



1 ' Beitrage zur Kenntniss des Sibirischen Cambriuni ' Mem. Acad. Imp. 

 Sei. St. Petersb. ser. 8, vol. viii, no. 10 (1898) p. 21 & pi. i, tig. 1. 



