340 PALEOZOIC PALEONTOLOGY. 
concave. ‘The entire lateral and anterior margin of the head is orna- 
mented with a continuous series of from twenty-five to thirty-five 
triangular, tooth-like processes, largest in front and decreasing regu- 
larly in size to the genal angles. The surface of the glabella and 
those portions of the cheeks lying between the eyes and the glabella, 
except in the furrows, is covered with rather coarse, irregularly- 
arranged, circular tubercles, the outer portions of the cheeks, in- 
cluding the marginal denticles, being finely papillose. Thorax con- 
sisting of eleven segments, the axis a little less than one-third the en- 
tire width, plure extended into sharp, posteriorly-pointing spines. 
Pygidium subtriangular in outline, the posterior extremity pro- 
duced into a dorsally-curving, attenuate spine, a little less than one- 
fourth the total pygidial length. Axis depressed-convex, indistinctly 
subangular along its median line, about one-fourth the entire width 
of the pygidium at its anterior margin, its sides nearly straight, 
gradually converging to the obtusely-rounded posterior extremity, 
which lies a little anterior to the base of the posterior pygidial spine. 
Plure with no conspicuous marginal border, flattened above, be- 
coming rather strongly convex in the middle, and then sloping away 
to the lateral margins with a slightly convex surface. Axial seg- 
ments fifteen in number; pleural segments grooved, eleven in num- 
ber, curving rather abruptly backward as they approach the margin, 
the two or three posterior ones nearly straight. Each segment of the 
pygidium marked by a more or less irregular line of tubercles. 
The dimensions of a rather large but imperfect head of this species 
are: extreme width between genal angles, 60 mm.; length from the 
front to the posteror margin of the occipital segment, 31 mm. The 
dimensions of a pygidium are: length, 30 mm.; width, 24 mm. 
Remarks.—Broken fragments of the heads, pygidia and thoracic 
segments of this species are exceedingly abundant in the strata at 
the base of the Oriskany formation. By reason of the great abundance 
of fragments of this species and of Homalonotus vanuxemi, this bed 
has frequently been designated as “the trilobite bed.” In the more 
or less complete coalescence of the outer extremities of the first and 
second pairs of lateral glabella lobes, this species is allied to those 
Oriskany species which Clarke has described under the subgeneric 
name Synphoria.* 
* Mem. N. Y. State Mus., No. 3, vol. III., pp. 15—19. 
