PALEONTOLOGY OF NEW-YORK. 
Eyes of medium size, their summit less elevated than the glabella, ex" 
tending backwards to the line of the occipital furrow, composed of 
seventeen vertical ranges of lenses; the entire number of lenses in 
full-grown specimens about one hundred, and. varying in the specimens 
examined from ninety-three to one hundred and three. 
The axis of the thorax is prominent, and narrower than each of the 
lateral lobes ; the annulations furnished with a prominent node at each 
extremity. The lateral lobes are flat or somewhat concave towards the 
axis, the articulations bending abruptly downward from the middle to- 
v ards the extremities; each articulation strongly grooved, the groove 
extending beyond the curvature. 
Pygidium semicircular; the axis prominent, with about nine annulations; 
the lateral lobes having about five or six ribs, each with a groove 
along the centre. 
Surface of the glabella pustulose, and of the articulations granulose, with 
some larger granules or pustules. The crust is thin, and the interior 
of the glabella shows distinct cavities corresponding to the external 
pustules. Hypostoma broad hastate; the buccal extremity obtuse, with 
a minute central point. 
This species, after the Dalmanites pleuroptyx , is more common than any other 
trilobite in this group of strata. It is not unfrequently enrolled, though nearly all 
the specimens in this condition are imperfect. The separate heads, which best illu¬ 
strate the characters of this portion of the animal, are from the decomposed shaly 
limestone. 
This species resembles the Phacops fecundus of Barrande ; but the eyes are 
smaller, with a less number of lenses, while the head is proportionally less broad, 
and there are fewer ribs in the lateral lobes of the pygidium. It differs from the 
P. bufo in the transverse furrows of the glabella, which in that one are rarely de¬ 
fined; in the characters of the eye; and in the prominence of the tubercles at the 
extremity of the annulations of the axis, as well as in the ribs of the pygidium, 
which are more bent backwards in this one. The'crust of the thorax in the P. bufo 
is more finely granulate, and the axis less prominent. 
Fig. 15. An entire specimen which has the head compressed from above, and the eyes a little 
distorted. 
Fig. 16. View of a specimen which is enrolled. 
