2 



BllITISH FOSSILS. 



central part is necessarily raised, so as to be nearly on a level with 

 the glabella. 



The cylindricarl eyes are on the most convex part of the cheeks, 

 and are directed outwards, scarcely forwards. The margin is 

 distinct in front of the head as a very narrow prominent ridge, and 

 furnished on each side with about 14 truncate spines ; the cheek 

 spine is directed backwards, and but slightly outwards, abrupt at its 

 origin, and not reaching beyond the two or three first body rings. 

 Tlie facial suture cuts the outer border in a direct line from the 

 base of the eye. 



All the prominent parts of the head are covered with larger and 

 smaller tubercles ; they only fail on the deeper fiirrow\s, and the 

 truly vertical outer half of tlie cheeks. They are conspicuous on 

 the border, and even on the cheek spines. 



The body and tail united are slightly longer than the head, the 

 thorax of 1 0 rings many tiiYies longer than the short square tail, 

 and the axis about one-fourth the whole width, and highly convex, 

 especially in front. There are no axal furrows to separate the 

 gibbous axis from the horizontal portion of the pleurse, and these 

 soon curve downward, and are abrupt and steep on the sides. 



The pleurse are semi-cylindrical, the front portion, separated b}^ 

 the pleural groove being very narrow in this and allied genera, 

 placed on the forward margin, and scarcely visible.* The apices 

 curve much backward, and in the hinder pleurae a little outward 

 again, and are produced into strong spines beyond the ovate facetted 

 portion. And all along these pleurae and over the axis tubercles 

 are placed at equal distances, except that the central prominent 

 tubercle fails on altei'nate rings of the axis, and the intervening- 

 ones, especially the ninth, are stronger than any other tubercles, 

 and remind us of the spines on Encrinurus. 



The tail is nearly square, concave rather than flat, the short 

 conical axis, of four rings, not easily distinguishable from the sides, 

 which are composed of three flat broad spinous pleurae directed back- 

 wards, and quite parallel, so as to give a comb-like appearance. 

 A few tubercles are scattered on the surface. 



Locality and Geological Position.- — Caradog Rocks, near Bala, 

 N. Wales (fig. 5) ; Woolhope Limestone and Shale, Gorton, 

 Presteign (figs. 1,2); V/enlock Limestone, Dudley and Malvern. 



* Yet I doubt the propriety of making this character so important in classification as 

 BaiTande has done. The pleural groove is always present in one form or another. In 

 this case it is anterior, in Cheirurus it is very short and oblique. 



