1896. | NEW YORK ACADEMY OF SCIENCES. 213 
In the P. Davidis sub-zone.—Fallaces A. Acadicus var. de- 
clivus—Parvifrontes. A. parvifrons—Longifrontes. A. Davidis, 
A. fissus, var. trifissus, A. punctuosus—Levigati. A. levigatus 
var terranovicus, var. ciceroides and var. mammilla, A. nudus. 
AGNOSTUS REGULUS. (Plate XVLI., figs. la, b and c.) 
Agnostus regulus. Trans. Roy. Soc. Can., vol. iii., pt. iv., 
p. 67, pl. vii., figs. 1 a—c. 
Amended Description.—Body elongate-elliptical, with straight 
sides and semi-circular ends. 
Cephalic shield elongate, semi-elliptical: posterior contour 
broken by the projecting glabella and narrow occipital ring. 
Width and length of the head shield nearly equal. Dorsal fur- 
row distinctly but not deeply impressed. Marginal furrow and 
fold are sharply defined, and the latter diminishes toward the 
posterior angles of the shield. 
Glabella large, consisting of two lobes; the anterior semicir- 
cular, wider than the posterior lobe, elevated above the general 
contour of the surface, and in some examples undulate with 
broad furrows, spreading from the back of the lobe; posterior 
lobe flattened-cylindrical, with a broad, faint transverse furrow, 
one-third from the front, interrupted at the summit of the gla- 
bella by a small tubercle, elongated on the line of the axis. 
Basal lobes obsolete, being merged in the posterior marginal 
fold. Occipital ring minute, narrowly lenticular, concealed be- 
low the projecting obtusely angular end of the glabella. The 
cheeks are narrowed in the middle, there being a crescent-shaped 
limb in front of the anterior lobe of the glabella, and a broad 
rectangular limb on each side of the posterior lobe of the gla- 
bella. 
The thorax consists of two segments ; the anterior subarcuate 
and marked by five lobes that are bounded by furrows radiating 
backward; the inner pair of lobes are larger than the outer. 
The posterior segment of the thorax is unknown. 
The pygidium is elliptical, with straight sides, and is trun- 
cated in front of the side lobes; it is widest at the anterior 
angles. The rachis is large, high, obtusely clavate, constricted 
in the middle, and divided into three lobes; the anterior lobe is 
narrow, especially in the middle; the middle lobe is short and 
sublenticular in form and bears an elongated ridge like tubercle 
on the apial line that projects backward across the anterior seg- 
ment of the third lobe; the third lobe is subpentagonal in form 
and has a pair of side furrows in the widest part. The lateral 
lobes of the pygidium are narrowed opposite the posterior part 
of the rachis and meet behind it. 
