324 Foint Levi Fossils, 



which the last two are sometimes blended into one. The an- 

 terior margins of the side lobes are almost at right angles to the 

 axis for one-half or thereabouts of the width, then sloping back- 

 wards to the outer corners, which they reach at an angle of about 

 SO*^ to the transverse diameter of the body. 



Just behind the margin there is a single groove, obscure to- 

 wards the axis but more distinct outwards. There are in some 

 specimens, several faintly marked ribs, but in general the side 

 lobes, with the exception of the anterior furrow, are smooth. 



Length of head of a specimen of medium size, seven lines 

 width, twelve lines ; distance between centres of eyes, seven 

 lines. 



Length of a pygidium of medium size, six lines ; width, twelve 

 lines ; length of axis, four lines and a-half ; width of same at 

 front margin, three lines and a half, and at half a line from the 

 posterior extremity, three lines. 



I have seen the underside of the head of this species and the 

 sub-rostral fold is distinctly divided as in A. platycephalus 

 Had not this character been observed, I would have, without much 

 hesitation, referred the head to the genus Ulcenus. 



In Limestone No. 3. 



ASAPHUS GONIURUS. N. s. 



The above name is proposed for a small triangular pygidium 

 found in No. 3. It is evidently distinct from any described Si- 

 lurian species of this country, but allied to one that occurs in 

 the Chazy Limestone at Mingan. The form is triangular, the 

 length three-fifths, or thereabouts, of the width, the axis scarcely 

 at all elevated above the surface, and indistinctly divided into seg- 

 ments in the anterior half, but towards the extremity becoming 

 strongly elevated, smooth and pointed. The largest specimen 

 seen is about lialf an inch in length. It resembles t e tail of a 

 small Homalonotus, 



Limestone No, 3. 



