﻿Vol. 66.'] THE CAMBKIAX KOCKS OF C03ILET. 37 



Axial furrow. — Practically obsolete. The glabella is well- 

 defined from the cheeks by the change of vertical curvature, but is 

 less distinctly marked off from the frontal limb. 



Fixed cheek. — Highest near the glabella; sloping down in 

 a uniform curve to the eye-lobes and to the front; extending 

 anteriorly beyond the ocular ridge and merging into the frontal 

 limb ; posterior limit marked by a rather steep downward curve. 



Eye-lobe. — From a quarter to a third of the length of the 

 head-shield ; situated opposite the middle of the length of the 

 glabella and occipital segment combined ; distance from the glabella 

 equal to the diameter of the latter; not raised at the outer 

 edge. 



Ocular ridge. — Beginning near the glabella in advance of 

 the anterior glabellar furrow, and curving outwards and backwards 

 to the eye-lobe. 



Frontal limb. — Sloping at a very gentle curve downwards all 

 the way ; having usually (but not always) a wide, slightly thickened 

 marginal rim, the surface of which has a slightly increased slope 

 •downwards and a delicatelj' raised inner border. 



Postero-lateral limb. — Consisting of a groove, widening 

 outwards ; and a raised border, with a geniculation at a distance 

 •outwards rather less than half the width of the glabella. 



Facial suture. — Owing to the bending down of the sides of 

 the cranidium, it is a little difficult to make out the exact form and 

 posit ion of the suture as viewed from above. 



The anterior branch runs more or less directly forward from the 

 eye, curves round rapidly inwards to meet the front margin, and is 

 never farther out than the eye-lobe. 



The posterior branch seems to vary slightly ; it follows a sigmoidal 

 ■course from the eye-lobe to the posterior angle of the cranidium, 

 which is well rounded and usually rather farther out than the eye- 

 lobe itself. 



Test. — To the unaided eye the surface is almost smooth, but 

 under a strong lens it proves to be finely granular, and, in one 

 instance at least [14-1], a number of minute tubercles are to be 

 ■seen. On the extreme front edge of the same specimen, the 

 granular surface is seen to merge into one of fine raised lines 

 6ubparallel to the border. 



Owing to the mixture in the rock of the free cheeks and frag- 

 ments of thoracic segments of this species with those of Agraulos 

 .(Strenuella) salopiensis, the correlations given below are somewhat 

 inferential. 



Fkee cheek. — There are several examples in my collection of 

 the remarkable free cheek represented in PL V, fig. 8. The facial 

 suture in the specimen [1G3] seems to be partly preserved, but 

 the eye, which was considerably elevated above the plane area, is 

 broken away. 



The plane area is small, and the genal angle is produced into a 

 very long and delicate spine of oval section, and stands out away 

 from the head- shield at an angle of 30° to 40° with the axis. 



