from the Cincinnati Group of Ohio. 427 
sharp spines, that extend back nearly or quite the entire length 
of the thorax ; glabella a little less than one-third the breadth 
of the posterior part of the head, separated from the cheeks on 
each side by a well defined furrow, but without having the 
neck furrow behind distinctly marked ; other characters of the 
glabella unknown ; eyes sublunate, nearly their own length in 
advance of the posterior margins of the cheeks. 
Thorax apparently shorter than the head, showing in the 
specimen examined only seven segments (one or two being 
probably concealed by the slipping backward of the cephalic 
shield); mesial lobe moderately prominent, scarcely equaling 
the breadth of the lateral lobes anteriorly, and tapering more 
rapidly backward, with its segments not arching forward. 
Lateral lobes less convex than the middle one; pleurs nearly 
straight and transverse, and furrowed for a little more than half 
on out, with their outer extremities merely rounded in front, 
and nearly rectangular behind, without any distinct backward 
curvature, 
Pygidium subsemicircular, scarcely one-half as long as the 
cephalic shield, and provided with a smooth flattened margin; 
mesial lobe moderately prominent, narrower than the lateral, 
tapering posteriorly, where it terminates rather abruptly, with- 
out passing quite upon the flattened margin, showing only very 
obscure traces of five or six segments on its anterior half. 
Lateral lobes more depressed than the mesial one, and wit 
flattened margins rather more than one-third the breadth at the 
anterior end of each, and each showing obscure traces of six or 
Seven furrowed segments. ’ 
Entire surface smooth. 
ngth of a specimen apparently very slightly shortened by 
the slipping of the cephalic shield a little back wpon the thorax, 
0°33 inch ; breadth at the widest part across the posterior part 
of the head, 0-25 inch; length of head, 027 inch; do. of 
pygidium, 0-11 inch. 
Until T saw the published figure of Proetus eects Hall, 
Thad thought it possible that this might be the same, although 
it did not seem to agree in several characters with those men- 
tioned in the previously issued description of that species. On 
comparing it with the figure of that form, however, it will at 
ae € Seen to present well marked differences. In the first 
pace its cephalic shield is decidedly longer in proportion to its 
Teadth, and more narrowly rounded in front; while the pos- 
terior lateral spines of its cheeks are nearly or quite twice the 
Proportional length of those in P. parviusculus. Its eyes are 
