180 ■:- 



rior margin, an angle of about 100° ; axis short, about half the whole 

 length, moderately convex, not very strongly defined at the apex, but still 

 distinct. Surface punctate. 



Length of the best preserved head in a straight line, not following the 

 curvature, 6 Hnes ; width at the posterior margin to the extremities of the 

 spines 16 lines ; width between the apices of the eyes 14 lines ; width of 

 the posterior half of the glabella 3 hnes ; and of the anterior half 6 lines ; 

 height of the head 6 hnes ; height of the ocular cones about 2J hnes ; 

 diameter of the same at about half their height 1 hne. 



Another specimen, consisting of the thorax and pygidium in connection, 

 but without the head, gives the following measurements : 



Length of the thorax 5 lines ; entire width 10 hnes ; width of the axis 

 3J hnes. 



Length of the pygidium in a straight hne from the anterior to the pos- 

 terior margin 5 lines ; width between the posterior angles 8 lines ; 

 between the anterior angles 6 hnes. The pygidium is rather strongly 

 convex. 



I. conifrons has the posterior portion of the glabella proportionately 

 more narrow and prominent, and the front conical instead of rounded. 

 These two species, however, are most closely allied. 



Locality and Formation. — Mingan Islands ; Chazy. 



Collectors. — Sir W. E. Logan ; J. Richardson. 



Sphaerexochus parvus. (N. sp.) 



S. parvus. — Billings. Geology of Canada, p. 133, fig. 66. 



Fig. 161. 



Fig. 162 



Fig. 164. 



Fig. 161. — Sphisrexochus parvus, a, side view of the glabella ; 6, upper side. 

 162. — Cheirurus Pompilius. The glabella. 

 163. — Lichas Minganensis. a and b, glabellfe of two individuals. 

 164. — Remopleurides Canadensis. The glabella. 



Description. — Head exceedingly convex, a little more than half of a 

 sphere, length and vridth about equal ; posterior glabellar lobes ovate, per- 

 fectly isolated, about one-third the width of the glabella ; middle and 

 anterior glabellar furrows visible only on close examination, each extend- 



