6 [230] A, Winchell on Fossils from the 
lobes, a farrow passes quite across the glabella, being curved 
backward in the middle. Behind this is another nearly parallel 
furrow, and in front is a pair of faint furrows situated nearly op* 
posite the anterior extremity of the palpebral lobe, and each 
traceable about one-third the distance across the glabella. An¬ 
other glabella, very similar to this, shows three transverse fur¬ 
rows, besides the anterior interrupted furrow. 
A finely preserved pygidium presents a strong convexity, 
especially in the middle lobe. Aside from the marginal flap, the 
external outline is nearly semicircular, with the anterior margin 
considerably curved. The lateral lobes are strongly convex, be¬ 
coming less so nearer the border, and abruptly joining the cau¬ 
dal flap, at an inclination of about 45°. The pleurae are furrowed 
in such a manner that there seems to be an accessory pleura be¬ 
tween each two principal ones. The articulations are seven in 
number in both the axial and side lobes, and extend nearly to 
the terminal apex of the middle lobe. The caudal flap is flat, 
and about as wide as the middle lobe at its anterior end, and 
marked uniformly through its whole length by eight or more 
rigid concentric strise. No indications of caudal spines. 
This pygidium was original^ referred to this species on such 
information as was accessible, amongst which was Hall’s figure 
in the Wisconsin Report (p. 22, fig. 4), showing indications of a 
similar striated caudal flap. I am not able by the help of Prof. 
Hall’s last memoir to change the reference, although I perceive 
the pygidium does not fully agree with the complete characters 
now published. I am inclined to think this pygidium has not 
previously been described. 
Ptychaspis Barabuensis, n. sp. 
The collection embraces some fragments of the cephalic and 
caudal shields of a large trilobite, which, while its generic rela¬ 
tions are somewhat indeterminate, has a certain expression which 
is peculiar. The head is about 2’4 inches broad, and rather con¬ 
vex ; the thickened and convex margin of the border is separa¬ 
ted from the glabella by a narrow, concave furrow, giving the 
border a width of three-tenths of an inch. Posteriorly, the bor¬ 
der is continued in genal points which attain a length not less 
than three times the length of the glabella. The movable cheek 
is swollen and separated by a deep transverse furrow from the 
posterior borders of the cheek. The surface is feebly scrobicu- 
late-wrinkled; though with oblique light it is seen to be dis¬ 
tinctly so, and the character is even better shown with a low 
magnifier, though the cast is preserved in sandstone. 
The pygidium which undoubtedly belongs to the same spe¬ 
cies is 29 inches across, and three-fourths of an inch in height. 
The middle lobe is nine-tenths of an inch across, and is quite 
