but is only one-fourth the size: its length is about half the greatest 

 width, the anterior angles truncated, all the rest of the margin broadly 

 and uniformly rounded ; axis gently convex, extending half the length, 

 narrowed to a point at the apex, where it is sometimes obscurely denned 

 all round. Surface covered with coarse undulating striae. 



Length of a perfect head following the curve 8 lines ; length from the 

 posterior margin to a straight line erected vertically from the front margin 

 4i lines ; width in a straight line between the cheek angles 9 lines ; width 

 of the glabella 4 lines ; length of the posterior margin of the cheek out- 

 side of the eye 3 lines. 



Length of the largest pygidium seen 4 lines ; width of the same 9 

 lines. A number of perfect heads and pygidia have been collected. The 

 largest head is the one above figured ; most of the specimens are one- 

 third smaller. 



On comparing a number of specimens of the head of both species, it is 

 found that this one differs remarkably from I. consobrinus in the form of 

 the glabella, the dorsal furrows being always straight, and either parallel 

 or with their anterior extremities a little more distant than the posterior ; 

 whereas, on the other hand, in /. consobrinus they are .never straight, but 

 always curved inwards anteriorly. This character must give to perfect 

 specimens a very different aspect, and will be found, most probably, cor- 

 related with other differences in other parts. The cheek angles are 

 somewhat variable in both species, but they are always prolonged back- 

 wards in _Z~. consobrinus, sometimes extremely so, as represented in the 

 above Fig. 320, e. In I. incertus they are, as a general rule, only a 

 little less than a right angle, while in some individuals they are rather more. 



Locality and Formation. Stanbridge, range 6, lot 20 ; Quebec group. 



Collector. -T. C. Weston. 



HARPIDES ? DESERTUS. (N. sp.) 



Fig. 321. 

 Fig. 321. Harpides ? desertus. An imperfect glabella. 



Description. Glabella conical, strongly convex ; sides nearly straight 

 or gently convex ; front rounded and abruptly elevated. Neck furrow 

 narrow, extending all across. Neck segment with a ^tubercle in the mid- 

 dle. The glabellar furrows are two deep elongate grooves extending 



