120 
PALEONTOLOGY OF NEW YORK. 
spines which reach as far as the fourth segment of the thorax. Posterior 
margin transverse. Surface moderately convex. 
Facial Sutures normal, approximating on the frontal margin. 
Glabella simple, elongate, sub-conate, sloping to a broadly rounded anterior 
extremity, which encroaches upon the frontal border. Length one-third 
greater than the width. Surface convex, longitudinally arched when nor¬ 
mally preserved. There are usually no traces of lateral furrows, but a single 
individual in which the crust is slightly separated from the rock and has 
become translucent, shows evidence of three oblique lines, apparently the 
second, third and fourth lateral furrows; the first pair being obsolete, and 
the fourth extending only part way across the glabella. Occipital lobes con¬ 
spicuous, transverse; occipital furrow narrow and sharply impressed, scarcely 
widening upon the cheeks; occipital ring broad, arched and somewhat fiat- 
tened, narrowing slightly to the genal angles. 
Eyes approximate, large, lunate, not elevated above the surface of the 
glabella; extending from the occipital lobes two-thirds the length of the 
glabella. Visual surface quite convex, particularly in young individuals. 
Palpebral lobe moderately large, sloping inward to the palpebral sulcus, 
which is sharply incised. 
Cheeks relatively narrow on account of the size of the eyes. Conspicu¬ 
ously grooved or depressed about the orbital ridge, and rounding more or less 
abruptly to the margin. The border is unusually wide and carries two paral¬ 
lel grooves, the outer of which is narrow and marginal, producing a beveled 
edge; the inner broad and shallow, becoming flat in old individuals. On the 
posterior border the margin is also beveled, and the genal spines are strongly 
ridged by the meeting of these beveled edges. 
Thokax transversely sub-rectangular, lateral margins slightly rounding and 
approximating posteriorly. Length to width as 2 to 3. Surface convex and 
strongly trilobate. Composed of ten segments. 
Axis arched, having more than one-third the width of the thorax; widest 
at the third or fourth segment, and tapering with slightly rounding margins 
