OF DENISON UNIVERSITY. 
63 
is bounded internally by a narrow, but deep groove, and terminates 
posteriorly in conically tapering genal points. The principal lobe of 
the glabella is relatively very large, convex, highest in the middle, 
widened anteriorly, circularly rounded in front, and gently curved on 
the sides ; no glabellar furrows are present. The complimentary [pos- 
tero lateral] lobes are large, oval, and project laterally farther than the 
main lobe. The surface of glabella finely, but sharply granulated ; 
margin finely striated. Size about as that of P. doris. Collected at 
Rockford, Indiana.” 
P. msignis, Winchell, is closely allied to P. meramecensis, Shumard. 
Not having access to the original description I can only gather that 
the head is armed with spines which reach twice the length of the 
glabella from the anterior end,” and the eyes are large, while the pi- 
gidium has a plane margin. 
P. howi, was described by Mr. Billings. It is said to be closely 
allied to the above, but has a greater number of annuli in the axis of 
the pigidium, which alone is known. 
P. vindobonensis, Hartt, is described as follows : 
“Pigidium semi-elliptical, very convex; (one or two segments 
appear to be wanting from the anterior margin of the only specimen 
seen,) but its width must have been greater than its length. Ten or 
eleven articulations are visible on the side lobes and twelve of the axis, 
which is very prominent and moderately tapering. The axial rings 
are depressed, convex, becoming smaller, more crowded, and more 
distant toward the apex. Ribs on the side lobes depressed, convex, 
decreasing in length, breadth and distinctness from before backward, 
while at the same time they become more and more inclined backward. 
The six anterior ribs preserved show a distinctly marked groove, origi- 
nating on the posterior margin at about one-third the length of the rib 
from the axis, and running obliquely, increasing in depth to the end 
of the rib. Smooth border none, or extremely narrow at the anterior 
angles, but becoming three-fifths the width of the axis near the poste- 
rior part of the pigidium, which is not visible in the only specimen I 
have examined.” 
We have here, therefore, a species described from a fragment of 
a pigidium, exhibiting neither end and nothing else of importance, 
an. example of puerility too often followed. 
