SILURIAN FAUNAS. 251 
rows longer than the second, indefinitely divided within and surround- 
ing a small tubercle on the side of the glabella; the posterior division 
directed more obliquely backward than the outer portion and continued 
as a slight, indefinite depression to the occipital furrow. Posterior 
lateral lobes large, subglobose. Occipital furrow rather narrow and 
deep across the axial portion of the head, becoming broader on the 
cheeks; occipital segment convex, broadest in the middle. Cheeks 
convex, the eyes opposite the second lateral lobes of the glabella. 
Pygidium subtriangular in outline, much elevated anteriorly, sloping 
abruptly to the sides and back; axis occupying about one-third of 
the width in front, bounded by the depressed, dorsal furrow, tapering 
gradually to the obtusely-rounded extremity which is close to the’ 
posterior margin of the pygidium; divided into about eight segments. 
Plure sloping abruptly from the axis to the sides, divided into five 
grooved segments. A small hypostome, which accompanies the speci- 
mens of this species and which probably belongs to it, is longer than 
wide, with the sides sinuate, making the middle portion much nar- 
rower than either of the extremities; the posterior margin is notched 
and the centre of the axial portion is elevated into a conspicuous, 
spiniform process. The entire surface of both head and pygidium, so 
far as preserved, except in the furrows, is covered with numerous, 
small, irregularly-arranged, rounded papille. 
The dimensions of the best-preserved head are: length, 14 mm.; 
width, 26 mm. Another much larger individual has a length of 23 
mm., but the width cannot be determined. The dimensions of a 
small pygidium are: width, 10.5 mm.; length, 6 mm.; convexity, 7 
mm. Some of the larger, fragmentary specimens of pygidia are fully 
twice this size. 
Remarks.—In his illustrations of this species Hall shows three 
sharply-defined pairs of lateral glabellar lobes. In the New Jersey 
specimens these three pairs of lobes may all be detected, but the . 
anterior pair is so inconspicuous as to be easily overlooked, and in 
no case has it been seen at all approaching the prominence given it 
by Hall’s illustrations. In his description of the species the anterior 
lobes are said to be minute, and it is probable that they were made too 
prominent in the illustrations. All the material representing the 
species from New Jersey is fragmentary and unsatisfactory for study, 
but there can be no doubt as to its correct identification. 
