ORDOVICIAN FAUNAS. 197 
in the New Jersey specimens. The small tubercle upon the occipital 
segment is not mentioned in the description of P. parviusculus, nor 
is it shown in the illustration. Another species allied to this one is 
P. alaricus Bill., from the Upper Ordovician of Canada. 
PROETUS BREVIMARGINATUS DN. Sp. 
Plate XY., Figs. 1-7. 
This species resembles the last in general form and size, but the 
heads may always be distinguished by the greater convexity of the 
glabella, with a deeply-impressed posterior pair of lateral, glabellar 
furrows and two anterior pairs of slightly-impressed furrows, also by 
the much shorter frontal border of the cranidium. The proportions of 
the head are broader, with broader free cheeks, and the tubercle upon 
the occipital segment is usually less conspicuous than in P. latimargi- 
natus. The pygidium which is believed to belong to this species has 
a broader axis, more broadly rounded posteriorly, than that of P. 
latimarginatus, and has a less number of segments on both axis and 
plure. 
The two species occur associated together in the same strata, and 
are about equally abundant. 
CYPHASPIS TRENTONENSIS 0D. Sp. 
Plate XV., Figs. 8-10. 
Description.—Glabella bounded on all sides by a deep furrow; the 
median lobe ovate or subpyriform, narrower behind, strongly arched, 
both longitudinally and transversely; basal lobes prominent, less than 
one-half the length of the median lobe and separated from it by deep 
furrows. The anterior marginal border of the cranidium narrow, 
bounded internally by a sharply impressed marginal furrow. Between 
the marginal furrow and the dorsal furrow bounding the glabella is 
a convex band, broader than the marginal border, which extends back- 
ward to the occipital furrow and surrounds the glabella, except pos- 
teriorly. The palpebral lobes are rather prominent and elevated, but 
do not rise as high as the glabella. Occipital furrow rather deeply 
