ORDOVICIAN FAUNAS. 199 
Remarks.—Only the pygidium of this species has been observed in 
New Jersey, but Billings’ illustration of a complete individual is 
introduced to show the characters of the remaining portions of the 
body. In Billings’ figure the broad, flat, posterior, axial rib of the 
pygidium is deeply divided for about one-half its length, although 
this division is not mentioned in the description of the species. In 
the New Jersey specimens no such bifurcation of this rib is noticeable, 
although just at the posterior margin of the pygidium there is the 
faintest suggestion of a median furrow. 
The surface of the test is marked by exceedingly fine, raised, con- 
centric lines, which arch forward in crossing the ribs of the pygidium. 
ARGES TUBERCULATUS MN. Sp. 
Plate XV., Figs. 11-13. 
Description.—Cephalon subtriangular to subpentagonal in outline, 
flattened above, the eye-lobes prominent. Glabella flattened above, 
its median and lateral lobes, as well as the eye-lobes, having the same 
elevation, strongly curved downward in front; median lobe broadest 
in front, its anterior portion strongly convex and extending beyond 
the lateral lobes; the second pair of glabellar furrows obsolete, the 
posterior and anterior ones continuous, separating off a pair of sub- 
ovate, lateral lobes, which are strongly convex in front, each of which 
is as broad anteriorly as the median lobe; the posterior lobes ill- 
defined. Dorsal furrows nearly as strong as the glabellar furrows 
anteriorly, but becoming fainter posteriorly and nearly obsolete before 
reaching the occipital furrow. Occipital furrow strongly impressed, 
curving forward medially. Occipital segment broad, its greatest 
breadth being back of the median lobe of the glabella. Fixed cheeks 
strongly convex. Hye-lobes prominent, placed about midway in the 
length of the head. Surface marked by scattered tubercles, which 
vary in size, being largest and most numerous upon the median lobe 
of the glabella. Free cheeks, thorax and pygidium unknown. 
In the best-preserved specimen the length of the head is 6 mm., 
the breadth between the eyes being 9 mm. 
Remarks.—But one other member of the genus Arges has been 
recognized in the Ordovician strata of America, Arges westenbergensis 
var. paulianus* from Minnesota. The New Jersey specimens differ 
* Pal. Minn., pt. II., p. 744. 
