38 
PALAEONTOLOGY OF NEW YORK. 
groove upon the surface. Border narrow at the sides, produced at the 
postero-lateral angles into two broad, stout, incurving cornua, whose inner 
bases are continuous and form an elevated marginal collar at the posterior 
extremity. The articulating ring and each pleural annulation, at its termina¬ 
tion upon the margin, bears a round, smooth terete, and gently incurved 
spine. These spines are shortest in front and increase in length toward the 
posterior cornua. The posterior collar has a width equal to that of the axis 
on its anterior margin, and bears a series of strong spines; one situated 
centrally, bifurcating at two-thirds its length, and, in a large individual, 
reaching a height of 10 mm., a short accessory pair of spines near the base of 
the foregoing (sometimes absent), a second and stronger pair at the beginning 
of the posterior curve, a third pair at the base of the broad terminal spines, 
and the incurved, elevated terminal spines or cornua, each of which bears an 
accessory spine near the apex. (See plate xv, figs. 1-3.) The height of the 
cornua in a large example is 12 mm. 
The Surface of the pygidium is covered with strong, sub-spiniform, irregu¬ 
larly disposed nodes. Upon the axis each annulation bears but a single row, 
but no arrangement in longitudinal rows is discernible. Upon the pleurge 
there is evidence of an irregular, double row of nodes, but at the lateral and 
posterior margins the nodes are more abundant and irregularly disposed. 
A single example having an irregularly nodose axis, and a central spine on 
the posterior collar, has the pleural nodes relatively small, abundant and 
arranged in two regular rows as in Dalmanites aspectans, affording evidence of 
the affinity of these two species in this respect. The characteristic orna¬ 
mentation of Dalmanites niyrmecophorus is however exhibited in pygidia 
varying widely in dimensions, the smallest individual noticed retaining this 
feature quite as strongly marked as the largest. 
A single large glabella which difiers from that of any known species of 
the Upper Helderberg group, may belong to this species. It has the general 
outline and contour of the glabella in typical Dalmanites, except that there 
is an apparent tendency to obsolescence in the second lateral furrows. The 
frontal lobe bears a pair of conspicuous nodes just behind its center, and a 
