90 PALEONTOLOGY 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, flattened near the longitudinal furrows for more than one-third 

 their width, rounding thence to the margin; conspicuously sulcate. 



PrGlDIUM 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 tlat annulations, which are depressed just within the marginal 

 furrows, and are gently recurved over the axial line. 



Pleura moderately broad and evenly convex. Annulations very indistinct, 

 three or foui - 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. 



Htpostoma sub-spatulate, verj convex, abruptly depressed and broadly auri- 

 culate on the antero-lateral margins. Anterior margin slightly refiexed; 

 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 mosl conspicuous upon the cephalon and the thoracic segments, but are 

 faint or obsolete upon the pygidium. 



