276 G. F. MATTHEW ON THE 
terior margin. A small fragment apparently of the under surface of the marginal area had 
dichotomous raised lines radiating toward the edge of the pygidium. 
Typ. B b (Fig. 14.) 
This pygidium is obcordate-trapezoidal and about one quarter wider than long. 
Axial lobe apparently more than half of the length of the pygidium ; its posterior 
margin merges into an elevated part of the marginal area which extends on the axial line 
to within a short distance of the posterior margin. The axial lobe has one distinct ring, 
and a second indistinctly marked ; a lunate segment about one third of the length of the 
front ring is divided from it by a sharply impressed furrow. 
Marginal third—The elevated part of the pygidium connected with the axial lobe is 
lanceolate in outline and traversed lengthwise by two low, narrow ridges, which meet 
near its extremity and enclose a small, lozenge-shaped area on the axial line, extending 
forward to the point of the axial lobe, where it is marked by a scar; similar scars extend 
along the centre of the axial lobe. The anterior part of the marginal third is impressed 
with grooves corresponding in appearance to the pleuræ; they originate at the ends of the 
axial furrows and extend backward beyond the posterior end of the axial lobe. The outer 
part of the marginal area is convex anteriorly and infolded as far back as the extremity of 
the axial lobe, where it spreads out suddenly, forming a sinus in the lateral margin. * 
There is also a wide shallow sinus at the extremity of the pygidium. 
Sculpture.—The surface of the axial lobe is smooth to the eye, but appears minutely 
granulated when viewed with a lens. The posterior third of the pygidium is marked by 
fiae parallel raised lines, scarcely visible to the naked eye; they are dichotomous at inter- 
vals, and are parallel to the posterior border, near which they are most distinct. The lower 
surface of the pygidium is marked by more distinct raised lines, which are parallel to the 
posterior margin. 
Type B c (Fig. 15). 
Pygidium broadly obcordate-orbicular, one-fourth wider than long. 
Axial lobe lanceolate, two-thirds of the length of the whole pygidium, moderately con- 
vex. Two rings distinctly, and a third more faintly marked off from the rest of the lobe. 
The anterior ring has a narrow lunate segment of the whole width of the axial lobe, lined 
off from the back by an arched furrow, lightly impressed. 
The marginal third is strongly impressed for two-thirds of its length by furrows origi- 
nating at the extremities of those which cross the axial lobe. There is a small tubercular 
elevation just behind the end of the axial lobe. The outer zone of the pygidium is convex 
in the anterior half, and broadly concave at the posterior rounded extremity, where also 
there is a shallow sinus about half as wide as the front of the axial lobe. 
Sculpture.—The posterior part of the marginal area has traces of closely set lines paral- 
lel to the margin. On the rings of the axis are rows of scars. 
Length, 1.1 inch; breadth, 1.3 inch. This is the largest pygidium among those 
examined, and, with the two preceding, was found at Portland, N.B., in the soft dark 

* This may be an accident of preservation and not characteristic of the form, 

