BY J. MITCHELL. 851 



and wide, and its lateral extension distinct. Neck ring and its 

 lateral extensions narrow, front border or limb reduced to a 

 sharp edge. Axial furrows relatively wide and shallow. Fixed 

 cheeks sub-reniform, very mildly convex; each bears a row of 

 about six tubercles longitudinally; anterior eye-lines well de- 

 fined, narrow, and surmounted with about five tubercles, of which 

 the anterior and posterior are most distinct. Free cheeks large, 

 depressed, subtriangular ; their front borders, mildly thickened, 

 bear about eighteen tubercles, some of them near the antero- 

 lateral angles being subulate but not spinate; furrows are faint, 

 neither borders nor furrows are present laterally; eyes small, 

 circular or conoid, fairly prominent, situated about midway be- 

 tween the anterior and posterior margins. Genal spines of 

 moderate length and nearly straight, directed horizontally out- 

 ward at an angle of about sixty degrees. Occipital spines ap- 

 pear to be equal in length to those of the genal angles, straight, 

 horizontally directed backward, and only mildly divergent. 



Obs. — The line of greatest width of this headshield lies just 

 behind the front border, and thence to the bases of the genal 

 spines its width diminishes. The posterior to anterior width is 

 12 : 17, and the transverse distance between the eyes from outer 

 edge to outer edge of each equals the posterior width across the 

 genal angles or spines. In outline this shield bears some re- 

 semblance to C. vogdesi E. and M. but in other respects, how- 

 ever, it differs from that species materially. For instance, in 

 C. vogdesi the cephalic spines are sub-erect for some distance 

 from their points of origin and then strongly arched and falcate. 

 Those of the present form are directed horizontally backward 

 and are nearly straight. In the former the neck spines, as & 

 very recently acquired and perfect cephalon of that species 

 shows, arise from the front of the occipital ring, but in the 

 case of the latter they arise from the posterior of this ring . 

 The occipital ring in the former is very wide, in the latter just 

 the opposite. The eyes in the former are near the anterior 

 border and directed outward at an angle of about 45°, depressed 

 and overhang the free cheeks; in the latter the eyes are situated 

 about midway between the anterior and posterior borders and 

 are erect. The greatest width of the cephalon of C. vogdesi is 

 aci'oss the medial line and behind the eyes; in the present form 

 it is anterior and in front of the eyes. This new cephalon also 

 resembles that of C. jacki E. and M., but the strongly spined 



