710 SILURIAN TRILOBITES, 



spines ; each pleura bears a number of large tubercles, usually 

 four, along the front margin of the ridge and two or three on the 

 posterior margin, two of them very persistent, one on the antei'ior 

 angle adjoining the axial furrows, and one on the posterior margin 

 a short distance from the axial furrow; these large tubercles (as 

 is the whole surface of the pleune) are covered with smaller 

 tubercles ; the tubercles from which the spines arise in the 

 posterior pair of jDleurte are very large. Axial furrow very 

 •distinct. 



Pyyidium. — Proportionately ver}' small and granulate, at least 

 four times wider than long, arciform. Axis consists of one rather 

 intensely arched ring; axial furrows distinct and deeply curving 

 inwards behind the axial ring ; side lobes slender, border indis- 

 tinct, lateral angles acicular and having a slight forward curve; 

 spines are seven in number, very strong, cylindrical, long, sub- 

 uniform, and strongl}' barbed and granulated, central one project- 

 ing from the axial ring. 



Obs. — On the nodes of the axis the granules sometimes become 

 confluent and form ridges parallel to the longer axis, and the 

 posterior pleural spines when decorticated are fluted longitudinally. 



The late Mr. Ratte was right in regarding this species as closely 

 allied to C. VemeuUi and C. veslcxdosa, Barr., but after careful com- 

 parison of ours with the figures of those species given by Barrande 

 we find it possesses so many features peculiar to itself that, in 

 our opinion, give it indisputable claim to rank as an independent 

 species. 



From C VernevAli it diff'ers (1) by the absence of the spines 

 along the anterior border of the cephalon and free cheeks; (2) in the 

 relative position of the genal spines and their much greater extent 

 and curvature; (3) by the barbed character of both of the pleural 

 .spines, the much greater size of these spines, and the vertical 

 nature of the last pair of principal pleural spines; (4^ by the 

 contour of the cephalon, which in C. VemeuUi has sharp 

 re-entering angles from the free cheeks, while in C. Vogdesi the 

 front margin is rather straight, projecting centrally, with greater 

 backward curvature at the front angles of the free cheeks. 



