224 TRANSACTIONS OF THE [may 18, 
shield semi-elliptical, about one-quarter wider than long. Dorsal 
furrow faintly impressed. Marginal fold and furrow strongly 
marked. Glabella elliptical-elongate, wider behind, rounded in 
front, in its widest part nearly a third of the width of the 
shield; narrowed at the base by two triangular lobes; a semi- 
elliptical lobe at the anterior end more than one-third of the 
length of the glabella. Occipital ring and posterior marginal 
fold narrow. Cheeks continuous in front of the glabella. Thorax 
of two segments; the anterior segment has five lobes, of which 
the outer pair are globose and the inner pair subtriangular and 
widest in front ; the center lobe is semi-circular, broad behind, 
and bears an elongate traverse tubercle in the middle. The 
posterior segment has three lobes, of which each of the two 
lateral ones is globose, and bears minute tubercles; the central 
lobe is subrectangular elongate, and the middle half is traversed 
by an arched furrow, which begins and terminates on the pos- 
terior margin of the segment. The pygidium is semi-elliptical, 
about one-sixth wider than long, and has the anterior margin 
arched forward. The marginal fold and furrow are about as 
distinct as those of the head shield. The rachis is oblanceolate, 
constricted in the middle, clavate, and pointed behind, about 
one-third longer than wide; it is traversed by two furrows, of 
which the one near the anterior end arches forward, and the 
other, near the middle of the rachis, arches backward. At the 
broadest part of the axial lobe there is transverse depression. 
The first segment of the rachis is narrow and elevated trans- 
versely ; the second segment is elevated lengthwise, having an 
elongated tubercle at the axial line that projects backward on 
the third segment; the third segment is triangular and depressed 
across the middle, and bears a small axial tubercle on the an- 
terior third. 
Sculpture.—The surface of the test in this species has a vel- 
vety appearance, and under the lens is seen to be covered with 
minute granulations, the surface also is rugulose or uneven, and 
the test thin and more apt to be distorted than those of the two 
preceding species. The parts of the body in this and the follow- 
ing Longifrontes are more frequently found connected than are 
those of the preceding species; and while in the species above 
described the two shields are often found doubled together, in 
this and the following species they are frequently spread at 
length. This species resembles A. scarabeoides of the Welsh 
Cambrian rocks, but has a narrower glabella with a more obtuse 
front. 
Length, 11mm. Width, 6 mm. 
Horizon and Locality.—In the fine dark grey shales of Div. 
1 d!, at Porter’s Brook, St. Martin’s. Infrequent. 
