Silurian Fossils of Canada, 67 



Cheirurus Icarus. N". s. 



Fig. 11. — Cheirurus Icarus, 



Description. — Oblong oval, proportional lengths of head, tho- 

 rax, and p3'gidium about as 3-^-, 6, 2. 



Head transversely sub-semicircular or sub-triangular, posterior 

 angles terminating in short spines. Glabella oblong, sides paral- 

 lel, obtusely rounded in front, neck segment elevated at the pos- 

 terior margin, neck furrow in its middle third narrow deep and 

 parallel with the posterior margin ; at each end for one third 'die 

 length sloping backwards. The posterior lobes of the glabella 

 transversely oval, completely isolated ; the median furrows lying 

 nearly in a line drawn across the glabella at mid-length, nearly 

 straight, at right angles to the longitudinal axis of the body, their 

 inner extremities separated by about one third the width of llie 

 glabella ; the anterior pair at a little more than one fourth the 

 length from the front, a litlle curved backwards and inwards. 

 The glabella extends the whole length of the head, being separ- 

 ated from the front margin by a very narrow groove only. 

 Cheeks depressed convex ; eyes rather small, nearly semicir- 

 cular at the base, situated their own lenglh from the posterior 

 margin and half their length from the sides of the glabella. The 

 neck furrow is extended in a sharp groove on the cheeks near 

 to and sub-parallel with the posterior margin, and appears also 

 to run round the sides of the head. 



Thorax nearly twice the length of the glabella, of eleven seg- 

 ments ; the axis less than one third the whole width, gently 

 tapering backwards ; the pleural groove short, in length about 

 one half the width of the axis, crossing the pleura) obliquely out- 

 wards and dow-nwards at an ansfle of about 45 o. 



The pygidium is about half the length of the glabella, com- 

 posed of three articulations, the backward curving extremities of^ 

 which form six short obtuse points. 



Surface not well preserved, but apparently somewhat smooth. 



This species apparently resembles C. himucronaius (Murchison),. 



