NEW SPECIES OF CAMBRIAN FOSSILS FROM CAPE BRETON. 
281 
To the movable cheek is attached the large globular eye, placed 
near the back of the cheek, the cheek is prolonged outward into a flat 
spine of abnormal size ; this spine is not narrower in the front quarter 
than the cheek itself, and curves backward in a regular arch at first, 
but toward the extremity becomes nearly straight. 
Of the two ribs which traverse it, one is an extension of the pos- 
terior marginal fold, and the other is a prolongation of the elevated 
middle part of the cheek. The flattened area on each side of the spine 
is a special expansion of the anterior and posterior marginal folds, and 
towards the tip of the spine, narrows more rapidly than the area 
occupied by the ribs ; of the flat areas, the outer is hollowed on the 
upper side, and the inner one somewhat convex, especially toward the 
base of the spine. 
A young hypostome, imperfect at the front, which may belong to 
this species, has a narrow, elevated obconical anterior lobe extending 
two-thirds of its length ; and an encircling, more depressed posterior 
lobe, occupying the rest of the hypostome ; both lobes are convex, and 
no border fold is visible. 
The pygidium of this species is broadly triangular, and has a strong 
obconical rachis of three segments, the third nearly as long as the two 
anterior. These latter have each an obscure lobe at the sides. The 
side lobes are narrow triangles, with a tubercle at the anterior outer 
corner. There is a distinct but narrow border fold at the sides and 
posterior end of the pygidium. 
Sculpture. — This is exceedingly minute and appears to consist of 
very fine granulations, with a smooth, shining surface on the front 
lobe of the glabella ; this part of the glabella shows occasional scattered 
small tubercles. 
Size. — Length of the middle piece of the head shield 3 mm. 
width, 5 mm. Length of the movable cheek, 3 mm.; width, exclusive 
of the genal spine, 2J mm. Width of the genal spine, 2J mm.; length? 
25 mm. Length of the pygidium, 1J mm.; width, 2 mm. Length of 
a young hypostome, 1J mm.; width, 1 mm. 
Locality and horizon. — Limestone bed in Div. 36 at Me Adam’s 
shore, Escasonie, C. Breton. 
This form is distinguished from the mutation Canadensis of S. 
alatus , found in the upper Cambrian shales at St. John,* by its long, 
Roy. Soc. Can, Trans , vol. xi, sec. iv, p. 107, pi xvii, figs. 11a and b anl 12a and b. 
