New Species of Tritobites. 379 



The distance of the eye from the dorsal furrow appears to be 

 at least greater than the width of the central lobe, but how much, 

 greater cannot be determined by the specimens yet discovered. 

 The facial suture cuts the front margin on a parallel passing 

 nearer the dorsal furrow than the eye. 



Judging from the fragments I have seen, this species must at- 

 tain the length of two inches. I think also that the eye must be 

 small and conical or sub-pedicilated, as it is in I. ovatus. It 

 clearly belongs to that group of Illaeni for which Mr. Conrad 

 proposed the generic name Thaleops. 



Locality and formation, — Mingan Islands, Black River lime- 

 stone ; appears to be abundant there in a fragmentary condition. 



Collector. — J. Richardson. 



Ill^enus clavifrons. (n.s.) 

 [Perhaps a variety of /. conifrons.] 



Description. — This species has much the form of I. conifrons, 

 but dinVs from it in having the unexpanded part of the glabella 

 one-fourth shorter and the expanded front portion depressed con- 

 vex instead of conical. The entire surface is coarsely punctured, 

 the punctures being smaller on the front part of the head than 

 they are on the posterior half. 



Locality and formation. — Mingan Islands, in both the Chazy 

 and Black River limestones. 



Collectors. — Sir W. E. Loo-an. J. Richardson. 



Ill^enus arcturus. (Hall.) 



Ill^enus Arcturus. Hall. Palaeontology of N.T., 

 vol. L, p. 23, plate 4, bis. Fig. 12. 



Specimens of detached glabellas agreeing very nearly with 

 Professor Hall's figures occur in the Chazy and Black River lime- 

 stones at the Mingan Islands. One of the fragments indicates 

 an individual three or four inches in length. 



Ill^enus orbicauda. (n.s.) 



Description. — The pygidium is sub-orbicular or including the 

 anterior lateral angles, a broad semi-oval, the length one inch, 

 and the greatest width thirteen and a half lines. The front margin 

 is tri-lobed, the middle lobe being convex, and nearly two-thirds 

 the whole width. The side lobes incline backwards at an ancle of 

 about 80° with the longitudinal axis; the fulcra] angle is at about 



