Vol. 67.] FROM THE PARADOXIDES BEDS OF COMLEY. 289 



Postero-lateral margin. — Consisting of a narrow convex 

 rim and a wide, well-rounded groove between it and the cheek ; 

 near the glabella the limb is almost horizontal, but farther out it 

 curves evenly and rapidly down to the postero-lateral angle, without 

 any decided point of geniculation. 



Front. — Consisting of a very narrow convex border in front, 

 widening somewhat outwards, and having a rather wide groove in 

 its rear. 



Facial suture. — Anterior branch, as seen from above (PL XXV, 

 fig. 1 «), convergent forwards and very short ; as seen from the side 

 (fig. 1 b) considerably longer and curved down to the groove 

 inside the marginal rim, beyond which it cuts the rim almost 

 horizontally. Posterior branch, as seen from above (fig. 1 a), 

 divergent and nearly straight to the postero-lateral angle, which is 

 situated distinctly farther out than the eye-lobe ; as seen from the 

 side (fig. 1 6), this branch is somewhat sigmoidal and rather long. 

 The two branches of the suture, as seen from above, are almost 

 in one straight line from the anterior to the posterior angles ; but, if 

 the cranidium were flattened out, or had lost its great convexity, 

 the posterior branch would have a wide outward extension. 



Test. — The whole of the outside of the head- shield is thickly 

 covered with short, irregular, subparallel, raised lines (PI. XXV, 

 iig. 5). These lines are longer on the front of the glabella than 

 on its posterior part ; on the cheeks they are much shorter ; while on 

 the frontal rim they are considerably elongated. It is just possible 

 to detect interruptions of the rugose markings at the sides of the 

 glabella where the lateral furrows would occur. The cheeks, taken 

 alone, might be described as granular ; but there is a distinct grada- 

 tion in the surface-characters from one part of the shell to another. 



In order to indicate the variations in size and in the shape of the 

 glabella, three additional figures (figs. 3, 4, & 5), drawn to the same 

 scale as the restoration of the cranidium, are given. 



Free cheek : One very imperfect fragment of a free cheek 

 from the Hill-House Flags shows that it bore a strong rounded 

 spine at the genal angle, set so as to project horizontally outwards 

 in agreement with the spines on the pleurae and pygidium. 

 ' Thorax : I have five or six specimens showing the pleurse ; of 

 these two of the most complete are illustrated (PI. XXV, figs. 6 & 7). 

 They consist, longitudinally, of three parts : a horizontal proximate 

 part, an inclined median part, and a distal spine that is nearly 

 horizontal. The length of the spine is about equal to that of the 

 proximal part, while that of the median part is rather less. The 

 pleurae have a well-rounded groove occupying one-half of the total 

 width. 



Pigidujm (PI. XXV, figs. 8a-Se): Size.— Moderate ; length, 

 exclusive of the spines, = 8 millimetres, greatest width = about 

 13 mm. 



General form. — Sub- semicircular, with a strongly convex axis, 

 convex side-lobes, and a flattened, horizontal, spinose border. 



General convexity. — About 1 : 3.5. 



