New Species of Trilobites. 369 



&nd the whole surface covered with strong undulating wrinkles. 

 The two species although allied and occnring in strata which are 

 most probably of nearly the same age are nevertheless decidedly 

 distinct. 



Judging from the figures given in the Palaeontology of New- 

 York I think it probable that neither of the species there referred 

 to /. crassicauda, are identical with the European form. 



The specimen represented on Plate 4 Chazy may be a frag- 

 ment of a large individual of this species but those on PI. 60, 

 Trenton, I think are not. I have never seen a fragment of the true 

 /. crassicauda in the Silurian of Canada. 



Associated with the specimen above figured is the head of an 

 individual of this species that must have been a little more than 

 three inches in total leno-ih. 



I beg to express my obligations to the Geological Society of 

 London for the loan of a specimen of the true /. crassicauda 

 with which to compare this species. 



Locality and formation. Mingan Islands, and also Island of 

 Montreal, Chazy. 



Collectors. Sir W. E. Logan, J. Richardson. 



IlLuEnus Bayfieldi. (N. s.) 



Fig. 4. 



Fig. 5. Fig. 6. 



Fig. 4. — Illcenus Bayfieldi. View of the thorax of a rolled up specimen. 

 5. — View of the head. 

 6. — View of the pygidium. 



Description. Oblong, distinctly trilobed ; length two or three 

 inches; width three fourths the length, central lobe rather more 

 than one third the whole width. Proportional length of head, 

 thorax and pygidium about as 9, 8, 6£. 



The head is transversely oval in outline, the width twice the 



Canadian Nat. 4 Vol. IV. No. 5. 



