3S3 



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 defined 

 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 maro-in 

 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 /. consohrinus 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 /. consohrinus they are never straight, but 

 always curved inwards anteriorly. This character must give to perfect 

 specimens a very different aspect, and Avill 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 L consohrinus, sometimes extremely so, as represented in the 

 above Fig. 320, c. 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 



