8 PALEONTOLOGY OF NEW YORK. 



frontal suture, thus Leaving a free median plate upon the epistoma, which is 

 elongate-sub-triangular in outline, attenuate at the apex, and recurved at 

 the base which forms the anterior portion of the prora. 



Glabella sub-quadrangular, broadest behind ; lateral margins slightly 

 incurving; angles rounded; length equal to three-fourths the length of the 

 cephalon. Surface depressed-convex. Lateral furrows in three pairs, the 

 first two of which are short, extending about one-fourth the distance across 

 the glabella, and are perpendicular to the margin. The third pair near their 

 proximal extremities are bent backward. The third or posterior lobes are the 

 strongest, the anterior or frontal lobe having about the same strength as each 

 of the first two pairs. Rarely in young individuals, and only under favorable 

 preservation, are these furrows and lobes to be seen, since they become 

 obsolete at an early stage of growth." 



Cheeks. The movable portions are flattened, and when normally preserved 

 are abruptly deflected. They have rarely been observed isolated, although 

 the cephalic shield is not infrequently seen with these parts wanting. 



Eyes situated at the summit of strong, elevated nodes, each of which 

 occupies nearly one-third the entire surface of the cephalon. These nodes 

 are bounded by low sulci separating them from the glabella, occipital ring 

 and lateral area. Visual surface small, lunate, covered with minute homo- 

 corneal lenses, of which about one thousand have been counted in each eye 

 of a small individual. Palpebral lobe capping the visual surface, and sloping 

 evenly and abruptly to the palpebral furrow. 



Thorax broad; length equal to the width. Surface depressed-convex, scarcely 

 trilobate ; lateral portions abruptly deflected ; margins approximating pos- 

 teriorly. 



Axis broad, making two-thirds the width of the body. 



Pleura narrow, deflected along their median line. 



Each of the segments is broadly rounded or flattened upon the axis, 

 lb" posterior margin infolding over the articulating ring of the next 

 succeeding segment. These articulating rings are exposed even where the 



