750 THE PALEONTOLOGY OF MINNESOTA. 
[Conolichas cornutus. 
narrower than it as to effect an abrupt indentation in the ante-lateral margin. Their 
posterior margin is slightly concave, and from this incurvature the cheeks are made 
to stand away from the thorax, as in Arges, etc. Their surface is convex and the 
slope rather the more abrupt on the posterior side. 
Thorax subquadrate, narrowing posteriorly, composed of nine segments, the 
first of which is obscured. Length of this part (entire), 20 mm.; anterior width 30 
mm. Axis proportionally broad; on the anterior segments having rather more than 
one-third the width of the thorax, but relatively narrower behind. Each segment 
is flat or depressed convex, and there are no nodes or thickenings at their junction 
with the axial furrow. The axis is regularly convex, and the lateral furrows broad 
and not deeply impressed. Pleurz flat for about one-third of their width, the outer 
moiety being evenly deflected. Segments broad, recurved and tapering to acute . 
terminations. 
Pygidium comparatively large, being 17 mm. in length, which is more than one- 
third the length of the entire animal. Axis very prominent, tapering gradually to a 
blunt protuberance at about two-thirds of its length, whence the surface becomes 
abruptly depressed, and the marginal furrows incurve, meeting on the posterior mar- 
gin. The elevated portion of the axis bears one distinct annulation, and a second one 
whose posterior groove does not extend to the axial furrows. The ribs of the pleure 
are in three pairs. Hach is broad, gently convex, the pleural grooves being narrow 
and sharply-incised. Adjoining ribs are united for rather more than one-half their 
length. The first two pairs are elongate lanceolate, curving backwards. Both of 
these pairs bear linear grooves on their surface. The members of the third or 
posterior pair are rhombiform, still with a slight inward curve toward the axial 
line. 
The surface is covered with fine and coarser tubercles or pustules, which are 
especially conspicuous upon the pygidium and axis of the thorax. There is no 
evidence of any other spine upon the test than that rising from the apex of the 
glabella. 
Formation and locality.—Middle Trenton limestone, Trenton Falls, N. Y. 
