70 SILURIAN TRILOBITES. 



eminente ; pleuris utrinque 4 cequalibus ovatis planis, apicibus omnibus ovatis retrorsis, nee 

 radiatis. 



A pretty species, which I was glad to recognize as an old friend, when Mr. Henry 

 Woodward called my attention to it in the British Museum. Ch. odolobatus had long 

 been described from the tail only ; but it was not suspected that it belonged to the section 

 Actinopeltis, and was so nearly allied to the Ch. davifrons as to make its separation a 

 matter of critical distinction. If it be the Cyrt. affinis of Angelin (he has only figured the 

 head in a side-view, and described it as smooth), our British name must give way to the 

 prior one, for it seems to be really the long-contested C. davifrons of Dalman. 



It is a small species, the three caudal shields known not indicating a fossil much 

 larger than one and a half inch long, of which the gibbous head occupies rather more 

 than a third, and is a little broader than the body, with steep, almost vertical cheeks, 

 which, measured in their own full width, are equally wide with the glabella, but do not 

 appear so in a front-view. The glabella is oval-oblong, blunt in front, and rather broadest 

 there, where it overhangs a narrow, very distinct margin. A line taken from front to 

 back is regularly convex, and the glabella is much elevated, both above the front margin 

 and the narrow neck-segment. The glabella-furrows are a basal pair, which completely 

 surround the rotund-oval basal lobes, only somewhat fainter where they join the neck- 

 furrow ; and two upper pairs, rather long, placed at equal distances, the middle furrow 

 being about the length of the basal lobe apart from it, and as remote from the front one. 

 The front furrow comes thus very forward, and on a line with the deep marginal furrow 

 of the cheek, opposite the notch between the facial suture and this margin. The cheek 

 is rudely triangular, strongly margined all round (spinose, probably, at the head-angles), 

 and with the very small eye placed on the side of the declivity, and a good way in advance 

 of the middle of the cheek, opposite the ocular furrow. The free cheek is small and trian- 

 gular, bisected by the deep marginal furrow. The cheeks are scrobiculate all over, the 

 glabella covered with fine granules, and scattered larger tubercles, very equally. 



Body-segments eleven, with a broad axis, equal to the pleura?, and only abruptly 

 tapering in the two or three last segments. The pleurae semicylindrical, the posterior 

 portion being so broad and convex as to occupy nearly the whole width of each, 1 the 

 fulcrum placed rather far out, and the pleurae then bent downward and a little backward, 

 facetted distinctly, and ending in a point. The hinder ones are most bent back, and 

 follow the curve of the tail-border. 



Tail transverse-oblong, nearly rectangular, the segments ending regularly behind, along 

 a nearly straight line. There are four on each side, the front ones bent at right angles, 

 and all nearly equal, with bluntish ovate tips. No space between the two terminal ones. 

 The axis short, of two segments and a very small terminal portion. 



1 There is no central line in this, to indicate a pleural groove, as in Eccoptochile (and some species of 

 Actinopeltis). It would appear that this character is not even of subgeneric value in some cases. 



