70 
PALEONTOLOGY OF NEW YORK. 
Eyes small, remarkably elevated. Visual surface lunate, sub-semi-cylindrical, 
liomo-corneal. 
Thorax convex, arched upon the axis, depressed and flattened upon the pleurae. 
Composed of nine segments. 
Axis having less than one-third the width of the body; margins sub¬ 
parallel. 
Upon the pleurce, the elevated limb of each segment is produced into a long 
marginal spine, sometimes equaling the width of the thorax. In front of 
this spine, upon each segment, is a short, bifurcate marginal spine, which is 
visible only when the posterior spine is broken away. 
Pygidium short, lunate. Anterior margin straight. 
Axis abruptly terminating just within the posterior margin in two nodes 
or tubercles. In addition to the strong articulating ring, it bears a single 
annulation which extends across the pleurm and is produced at the margin 
into long spines. Anterior to this pair of spines are three pairs, of which 
the first is shortest, and belongs to the articulating ring. There is also a 
single pair on the terminal border, making in all ten marginal spines upon 
the pygidium. 
Pleura flat. 
Surface ornamented with tubercles, which are crowded upon the lobes of 
the glabella, and irregularly disposed upon the cheeks. The segments of 
the thorax each bear a single row of strong tubercles, there being from two 
to four longitudinal rows upon the axis, and two longitudinal rows upon the 
pleurae. Upon the pygidium there are tubercles on the annulation, at the 
bases of the marginal spines, and at the termination of the axis. 
Dimensions. The smallest individual observed has approximately a length 
of 10 mm., a width of 6.5 mm., and the largest a length of 21 mm. and a 
width of 14 mm. 
Observations. There is a similarity in the more general features between 
this species and Acidaspis tuherculatus, Conrad, from the Lower Helderberg. 
