228 TRANSACTIONS OF THE [May 18, 
elabella. The occipital ring is narrow, and is concealed beneath 
the projecting posterior extremity of the glabella. The cheeks 
are somewhat full, especially in front, and are divided by a fur- 
row that connects the dorsal and marginal furrows, and each 
cheek is seamed across by a fainter furrow. 
The thorax consists of two segments, of which the first bears 
five lobes; the two outer pairs of these lobes are globose, and 
the central one is semicircular and is crossed in the middle by a 
light furrow transverse to the axis of the thorax. The second 
segment of the thorax has three lobes, of which the two outer 
are somewhat elongate, and each is marked by a light furrow ; 
the central lobe is subrectangular, and is traversed by a fur- 
row angulated on each side of the axis of the thorax, and begin- 
ning and terminating on the posterior side of the lobe. 
The pygidium is subelliptical, and its width and length are 
about equal. The marginal fold and furrow are about as distinct 
as those of the head shield. The rachis is oblanceolate, nearly 
half as wide as the pygidium, and its length is about four-fifths 
of that of the pygidium ; it is narrowed in the anterior third, and 
is crossed in that part by two transverse furrows similar in ap- 
pearance and direction to those of the preceding variety. The 
included lobe bears an elongated tubercle ; the posterior lobe of 
the rachis is conical. The lateral lobes of the pygidium are 
moderately elevated and meet behind the rachis. 
Sculpture.—This variety appears to be smooth externally, but 
sometimes shows a granulated inner surface to the test; by its 
smoothness it is distinguished from the other Longifrontes that 
occur with it. 
Size.—Length, 13 mm. Width, 5 mm. 
Horizon and Locality.—Frequent in the fine dark shales of 
Div. 1d, 1. At Porter’s Brook, St. Martin’s, N. B. 
This variety differs from the type of A. gibbus in its narrower 
rachis and the peculiar second lobe of the pygidium. It is the 
most widely diffused of the Longifrontes in the St. John group. 
f Var. 
A few pygidia which by their general form, and in the lobation 
and contour of the rachis, appear to be of this species are found 
with the above form, but they are spined on the margins. We 
do not know the head shield. 
Dr. Henry Hicks’ description of A. scutalis of the Menevian 
group in Wales agrees closely with that of A. gibbus, except 
that the cheeks of the head-shields, and the side lobes of the 
caudal shield are said to be covered with tubercles. This ex- 
