ORDOVICIAN FAUNAS. 191 
ARTHROPODA. 
TRILOBITA. 
HARPINA OTTAWENSIS (Bill.). 
Plate XIV., Figs. 1-2. 
1865. Harpes ottawaensis Bill, Pal. Foss., vol. 1, p. 182, fig. 165. 
189%. Harpina, cf. H. ottawensis Clarke, Pal. Minn., pt. 411., p. 757, 
fig. 79. 
Description.—*Head strongly convex, with a wide, punctured border, 
which extends backward to about the thirteenth segment of the thorax. 
If a line be drawn across touching the posterior edge of the neck 
segment, the contour in front of that line is nearly a perfect semi- 
circle. Glabella regularly conical, its length about five-ninths that 
of the head; posterior furrows distinct, entering at about one-half the 
distance from the ocular ridge to the posterior margin of the neck 
segment, thence running obliquely inward and backwards at an angle 
of about 45°, apparently not quite one-third the width; two anterior 
furrows on each side, represented by obseure pits; neck furrow nar- 
row; neck segment convex, strongly elevated on the fixed cheeks. 
The eyes [ocelli] are small and situated on a line drawn across the 
glabella at the anterior fourth; ocular ridge well defined, smooth, 
prolonged, with a backward curve outside of the eye. Thorax a little 
more than half the width of the head; the axis strongly convex and 
gradually tapering backwards; side lobes flat; plure with a wide 
groove along the middle, a small portion of their outer extremities 
turned backward. Surface of thorax, glabella and a subreniform 
space on each side of the base of the glabella smooth; the border with 
circular punctures about [0.2 mm.] in width, and separated by smooth, 
rounded interspaces half their own width; the punctures larger and 
more distant at the inner edge of the border; on the elevated part 
of the cheeks they have a subreticulated arrangement.”—Billings. 
Remarks.—Fragments of the head of this species are not uncom- 
mon at Jacksonburg, but no perfect individual or even a perfect head 
has been observed. ‘The commonest occurrence of the species is as 
i 
