156 G. F. MATTHEW ON CAMBRIAN FAUNAS 
2.—SELENOPLEURA BOMBIFRONS, N. Sp. 

Fic. 5.—Selenopleura bombifrons, N. Sp.—Centre piece of the head shield. Magnified 
four times. 5 a. Same seen in profile. 5 b. Same seen in front. 
Under this name I propose to describe a small trilobite from Topsail Head, which 
seems nearer to this genus than to any other, though it combines characters which recall 
several other genera. Some of the features are such as might be looked for in the young 
of species of Selenopleura, but the shield, on which the following description is founded, 
seems to have attained its permanent features. In the long, cylindrical glabella, some- 
what wider in front than behind, and overhanging the anterior margin, it recalls the 
genus Dolichometopus, Ang., Linrs.; in its dorsal suture comparatively straight, and near 
the outer margin of the shield it approaches Agraulos and Conocoryphe. The general form, 
however, the granulated surface, projecting eyelobes, etc., seem to bring it nearer to 
Selenopleura than to any other genus. 
Only the centre piece of the head shield is known. This is small, and of a trapezoidal, 
semicircular form ; it is strongly elevated along the axis, and depressed at the sides and 
in front. The dorsal furrow is strongly impressed. The anterior margin is depressed, 
and is strongly arched backward near the suture, so as to narrow considerably the outer 
end of the anterior limb of the fixed cheek. There is a narrow, rounded fold to the 
anterior margin, and a distinct and moderately wide furrow behind it. 
The glabella is cylindrical, somewhat wider in front than behind, narrowest between 
the first and second furrows, prominently elevated for most of its length, and has flattened 
slopes ; it is depressed at both extremities, and is indented on the sides by three pairs of 
furrows, which are progressively longer from the posterior to the anterior; the former 
extends scarcely half-way to the axis of the glabella, but the latter, which is strongly 
directed forward, two-thirds ; the glabellar furrows are broad and shallow. The occipital 
ring is rather narrow, and is sharply divided off from the glabella by a narrow, deep 
furrow; it is somewhat pointed behind, and bears an indistinct tubercle on the middle. 
The fixed cheek, behind the ocular fillet, is subtriangular, moderately elevated 
toward the glabella, but depressed at the outer sides. The eyelobe is short, prominent 
and distinctly elevated ; the ocular fillet is broad, but not conspicuous. The posterior : 
margin is somewhat angulated upward in the middle, and is rounded forward at the 
outer angle: the marginal fold is narrow, and slopes forward to the furrow ; the furrow 
widens and turns forward as it goes toward the genal angle. 
The whole surface is covered with minute granulations, which are coarser and more 
conspicuous on the elevated parts of the shield than elsewhere: on the higher part of the 
glabella these granulations pass into imperfect ridgelets, which are concentric to the 
elevated portion of the glabella where they are most conspicuous; they are most distinct 
on the posterior third of the glabella. The backward flexure of the anterior margin of 
the centre piece of the head-shield indicates that this species had a narrow free cheek. - 
Length of the cephalic shield, 3 millimetres; width of the centre piece, 5 mm.; 
height, 2 mm. 
