372 New Species of Trilobites. 



with short squamose wrinkles, of which there are from six to 

 eight in one line. On the tail these seem to radiate irregularly 

 from the axis as a centre. 



This species is related to I. Bayfieldi, but differs in its propor- 

 tions, its head being larger and the axis of the thorax not square, 

 but longer than broad ; the eye is more distant and the surface 

 not smooth. /. crassicauda has a much larger pygidium, with 

 a conical axis, well defined all round. 



Locality and formation. — Trenton Limestone, City of Ottawa. 

 Specimens with all the parts in place rare, as indeed are all the 

 species except I. Bayfieldi. 



Illcenus Conradi. (N. s.) 



Fig. 1. Fig. 8. Fig. 9. 



Fig. 7. — lll&nus Conradi. View of the head of a rolled up specimen. 



The width of the cheek pioces cannot be seen in this view 



on account of the foreshortning. 

 8. — Illcenus Conradi. Pygidium of same specimen. 

 9. — Illcenus Conradi. Dorsal view, shewing the 8 segments of 



of the thorax. 



Description. — Oblong, distinctly trilobed, central lobe less than 

 one-third the width at the neck segment, the whole width three- 

 fourths the total length. Proportional length of head, thorax, 

 and pygidium, as 5 J, 4 J, 4. 



Head transversely sub-fusiform, the lateral extremities outside 

 and in front of the eye terminating in obtusely rounded points ; 

 width measured from point to point a little more than twice the 

 leno-th ; front margin convex along the middle with a gentle broad 

 concave sinus in front of each eye ; posterior margin strongly tri- 

 lobed by the dorsal furrows, straight from the furrow to the 

 bend of the pleurae, then curving backwards to a point behind 

 the eye and thence forward and outward to the lateral extrem- 

 ity. The dorsal furrows are deep and broadly concave at the 

 margin, but become obsolete at about one third the length of the 

 head.; they curve a little inwards and they are distant from each 

 other one-third the whole width of the head. The eye is small, 

 sub-globular, abruptly elevated all round the lower, outer and 



