﻿STAUROCliPIIALUS. 



85 



on each side with about fourteen 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. The 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 furrows and the truly vertical outer half of the 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 body of ten rings many 

 times 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 pleurae ; and these soon curve downward, 

 and are abrupt and steep on the sides. 



The pleurae are semicylindrical, the front portion, separated by the pleural groove, 

 being very narrow in this and allied genera, placed on the forward margin, and scarcely 

 visible. 1 The apices curve much backward, and in the hinder pleurae again a little 

 upward, 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 the alternate rings of the axis, and the inter- 

 vening ones, especially the ninth, are stronger than any other tubercles, and remind us of 

 the spines on Encrinurus, a genus not yet described in these pages. 



The tail is nearly square, concave rather than flat, — the -short conical axis of four rings 

 not easily separable from the sides, which are composed of three flat, broad, spinous pleurae, 

 directed backwards and quite parallel, so as to give a comb-like appearance. A few 

 tubercles are scattered on the surface. 



Locality and Geological Position. — Caradoc Rocks, Rhiwlas, near Bala, N. Wales 

 (figs. 19, 20). Woolhope Limestone and Shale, Corton, Presteign (fig. 18). Wenlock 

 Limestone, Dudley and Malvern. 



S. globiceps, Portlock. PI. VII, fig. 21. 



Ceraurus globiceps, Portlock. Geol. Rep. Tyrone, p. 257, tab. i, fig. 7, 1843. 

 Staurocephalus globiceps, Salter. Morris's Catal., 2nd ed. p. 115, 1854. 



— — Id. Decade 11. Geol. Survey, pi. v, fig. 6, 1865. 



S. ovafus, granosus, caudd utrinque elongatd, spinis divergentibus. Glabella stipite 

 brevi vix lobato. Oculi approximati. Spina genales et pleurales diffusa. Cauda brevis, 

 pleuris primariis longe extensis, latis ; reliquis — ? 



1 Yet I doubt the propriety of making this character so important in classification as Barrande has 

 done. The pleural groove is always present in one form or another. In this case it is anterior, in Chei- 

 rurus it is very short and oblique. 



