90 
PALAEONTOLOGY OF NEW YORK. 
Eyes proportionally large, reaching anteriorly almost to the marginal sul¬ 
cus. Orbital ridge well developed, its base lying lower than the surface of 
the cheek. Visual surface elongate-lunate. 
Thorax sub-quadrate, slightly wider than long. 
Axis broadly arched, having somewhat more than one-third the width of 
the body. Segments transverse, narrow, with vertical sides. 
Pleura battened near the longitudinal furrows for more than one-third 
their width, rounding thence to the margin; conspicuously sulcate. 
Pygidium sub-elliptical in outline, surface evenly sloping posteriorly ; length 
slightly less than twice the width. Border broad, limited within by a low, 
faint sulcus; convex toward its inner edge, sloping regularly outward, some¬ 
times slightly concave. 
Axis depressed-convex, relatively narrow, having less than one-third the 
width of the shield on the anterior margin; tapering rapidly to a broad, 
scarcely elevated extremity just within the marginal sulcus, behind which, in 
the axial line, lies an obscure node-like elevation; composed of eight or ten 
broad and fiat annulations, which are depressed just within the marginal 
furrows, and are gently recurved over the axial line. 
Pleurae, moderately broad and evenly convex. Annulations very indistinct, 
three or four of which and in rare instances a fifth may be counted on each 
side. These are all sulcate, the anterior and posterior limbs of the annula¬ 
tions having equal size. All the annulations become extinct at the marginal 
sulcus. 
Hypostoma sub-spatulate, very convex, abruptly depressed and broadly auri- 
culate on the antero-lateral margins. Anterior margin slightly retlexed; 
posterior and postero-lateral margins narrow and flattened. Posterior sulcus 
conspicuous. The centrum also bears a low sulcus on its posterior portion. 
Surface, on its more elevated portions, marked by scattered granules, which 
are most conspicuous upon the cephalon and the thoracic segments, but are 
faint or obsolete upon the pygidium. 
