92 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



The frontal lobe of the glabella, in well-preserved specimens, is nearly 

 twice as wide as long ; the anterior furrow is very oblique, and sharply 

 impressed ; the median furrow is nearly rectangular, sharply impressed, and 

 sometimes not reaching the longitudinal groove ; the posterior groove is a 

 little inclined backwards, and reaches the margin of the glabella ; the 

 occipital furrow, is well defined at the sides and upon the cheeks, but less 

 strongly in the centre. The occipital ring is strong and wide, prominent in 

 the centre, and sometimes rising into a tubercle or short spine. Eyes pro- 

 minent, rising much above the summit of the glabella, and, on that side, 

 sloping abruptly to the dorsal furrow : five or six, and rarely seven lenses 

 may be counted in the vertical line, and twenty-five rows ; the anterior and 

 posterior rows with two, three and four lenses. The lenses are prominent, 

 and surrounded by a depressed circular line. 



In the thorax, the axis is rounded, prominent, and a little narrower than 

 the lateral lobes ; the lateral lobes flat for half their width, and sloping ab- 

 ruptly to the margins. ( This character, and the convexity and comparative 

 width of axis, depend much on the degree of compression which the fossil 

 has sufl"ered.) 



The pygidium is broad, semieliiptical approaching to semicircular ; the 

 axis prominent and tapering to a rounded extremity, marked by nine or ten 

 (sometimes eleven or twelve) rings ; the lateral lobes marked by five ribs, 

 which are separated by a deep groove, and the summit of each marked by a 

 linear groove terminating at the border : the ribs are extended beyond in 

 flattened foliate expansions, which are gently curved backwards. The centre 

 or caudal prolongation is wider and shorter than the others. 



Surface granuiose or papillose ; and, upon the fimbriate extremities, the 

 papillae are elongated. 



In the larger specimens of pygidia, there are twelve or fourteen and even 

 sixteen rings. The fimbria are produced in wide lanceolate extensions, and 

 are strongly pustulose. When the crust is removed, there is a deep groove 

 limiting the extension of the ribs of the pygidium, and the impressions of 

 the fimbria are shown beyond this. A separated portion of the crust shows, 

 that at the base of these fimbria, the border is abruptly thickened with an 

 angular lower edge. The external surface presents some variations of cha- 

 racter which have not been noticed, so far as I know. The occipital ring is 

 often surmounted by a tubercle or spine, and the second ring of the axis of 

 the pygidium in like manner v sometimes several rings of the pygidium are 

 thus marked with more minute spines. Again we find the occiptal ring, all 

 the annulations of the thorax, and many of those of the pygidium, marked 

 by short spines. 



I am not yet able to determine that the presence or absence of these spines 

 is of specific importance. In the specimens heretofore described, the im- 

 perfection of the crust may have prevented the discovery of spines ; and 



it is scarcely possible to constitute a new species upon this character, from 

 strata whence three have already been described. 



[ September, 



