ADDITIONAL NOTES ON THE CAMBRIAN OF CAPE BRETON 419' 
AsAPHELLUS (?) PLANUS, H. sp. PI. XVIII, fig. 11. 
A broad oval species with smooth shield and prominent eyelobes. 
The head shield is semicirclar, with strong cheek spines. It is 
about twice as wide as long, and has a broad flat margin. 
The middle piece of the head shield is narrowed in the middle by 
the eyelobes being placed close to the side of the glabella. 
The facial sutures are strongly arched out in front of the eyelobe and 
turning meet along the front margin ; the front area of the cheek thus 
left, is wider than the middle piece at the eyelobe, and three-fifths of 
the width at the back of the middle piece. The suture curves out 
boldly behind the eyes, turning inward again near the posterior margin, 
which it cuts about a third of the distance from the outer margin of 
the head shield. 
The glabella is level with the cheeks, except at the front, where it 
slopes down to the flattened anterior margin. The eyelobes are 
strongly elevated, short, and placed about half way from the front of 
the shield. There is a minute tubercle on the axial line one-quarter 
from the back of the head. The posterior marginal furrow is short 
and shallow, and the occipital ring narrow and obscure. 
The movable cheek behind the eyelobe is nearly as wide as the 
glabella ; the front runs beneath the front margin of the middle 
piece in a wide semi-doubleur what extends to the axial line. Pos- 
teriorly, it is lengthened into a genal spine, which, from the facial 
suture to the point, is as long as the posterior extension of the suture. 
The movable cheek, under the eyelobe, carries a convex band of 
several rows of minute ocular facets arranged diagonally ; those in 
front of the middle of the band run diagonally upward and forward, 
those behind the middle run diagonally upward and backward. 
The thorax of eight joints has long, narrow segments, terminating 
in rounded points, strongly facetted ; the ring of the middle segment 
is about as long as the pleurie ; the pleura? are bent (but scarcely 
geniculate) at one-half of the length of the first segment ; they bear a 
quite shallow furrow directed backward ; each ring of the thorax has 
a narrow articulating band. 
A thorax and pygidium of smaller size, supposed to belong to this 
species, has the following characters : The pygidium is broadly semi- 
circular and no axis is visible; a slight broad protuberance one-third. 
