231 



There are traces of a very narrow anterior marginal fold, and behind 

 it a narrow convex anterior area of the cheeks. The glabella is quadrate, 

 rounded in front, and bears three pairs of furrows, which are progres- 

 sively less bent backward from the back to the front pair, though the 

 two posterior pairs are already parallel ; the anterior pair are quite faint, 

 and more strongly arched than the others. The glabella is somewhat 

 keeled along the axial line. The fixed cheek is long and quite narrow, and 

 is separated from the front area by a shallow furrow ; at the eyelobe it 

 is about one-third of the width of the glabella, and at the back about one- 

 half. The eyelobe is long, narrow and obscure. The posterior marginal 

 fold is narrow but prominent. The occipital ring is bent forward at the 

 ends, and has a tubercle on the axial line. 



Sculpture. This species has a smooth test, but under a small lens 

 shows a somewhat uneven surface. 



Size. Only one example known ; in this the middle piece of the head 

 is 6 mm. long and 10 mm. wide at the back. Scarce. 



Horizon and locality. Fine gray shale of Assise C 3 c 2 at McLeod 

 brook, Boisdale, N. S. 



This species is clearly distinct from T. Beckii, Green, by its narrower Compared 

 cheek and wider space between the sutures in front. It resembles more Wlt . ot " er 

 closely T. Angelini, Linrs, but it differs from the type of that species as 

 figured by Liunarrssou in the wider frontal area of the cheeks and its 

 convex front margin ; also in possessing three pairs of furrows, &c. 

 From the Norwegian form, referred to this species by Brogger, it differs 

 in its narrower glabella, rounded front, and in having three pairs of 

 furrows, though the third one is faint ; the anterior area of the fixed 

 cheek is wider, and is separated from the rest of that cheek by a shallow 

 furrow ; it is, however, nearer this form than to any other known to me. 



Billings does not describe T. Fischeri, except by contrast with other 

 species (Upper Ordovician chiefly), but from his figure of that species, the 

 Cape Breton form differs in the posterior marginal fold, which is not 

 turned forward, like T. Fischeri. It also differs from that species in hav- 

 ing an anterior buccal area, and in the absence of pits on the front of the 

 glabella.* 



I refer this species to Triarthrus rather than Parabolinella because of 

 the narrow fixed cheeks, the long, backward turned eyelobes and the 

 regular, straight furrows on the glabella. 



Palseoz. Fossils, vol. 1, p. 291, fig. 280. 



