37 
The glabella is prominent and almost spherical in the anterior portion, 
while the posterior is mucli less elevated and narrow, and seems to have acted 
as a peduncle ; it is bounded by deep but rather narrow dorsal furrows ; this 
peduncular portion, which is separated from the spherical part by a single 
transverse furrow, situated immediately behind this part, has two lateral 
furrows which do not reach the centre. 
The fixed cheek is slightly arched and folded transversely. The eye is 
small and projecting ; the free cheek is very small, but the state of preservation 
will not admit of my giving either its shape or boundary. 
The outline of the head is semi-oval, and bounded by a rather narrow 
ridge situated in front of the glabella, which completely hides it. This ridge 
is prolonged posteriorly into genal spines, fairly acute, although thick, and 
provided on the upper surface with two vertical spines, the more prominent 
of which is near the genal angle, and the other is much smaller and almost 
immediately below the first mentioned. 
The thorax is unknown to me. 
The j)ygidium is very remarkable ; the axis is elongated, narrow, 
and made up of seven segments. The surface of the lateral lobes is slightly 
convex. The segment of the axis gives rise to a rib which is prolonged to a 
considerable length, slightly curved, and its base makes almost a right angle 
with the dorsal furrow of the axis ; immediately below this prolongation 
another a little longer is developed with a more oblique direction, and which 
forms an acute angle with the first. By this arrangement the j3ygidium 
aj)proaches that of some species of Cheiruriis and Acklaspis. As its surface is 
quite smooth it is probable that that of other portions of the animal will be 
so also. 
Helatlons and Differences, — In the form of the glabella and in general 
characters this species has considerable resemblance to StaurocepJmhis unicus, 
W. Thomson, but differs from it in the folding of the cheeks, and the form 
of the pygidium. In this latter point it approaches somewhat Staurocephalus 
glohiceps, Portlock. It cannot, however, be confused with this species, as the 
pygidium is provided with two spines only, instead of four. 
