754 THE PALEONTOLOGY OF MINNESOTA. 
[Proetus parviusculus. 
HopPLoLicHas, Dames,—Frontal and lateral lobes equally convex; occipital lobes present. Occip- 
ital ring with median simple or forked spine. No typically developed representative of this 
group is known to occur in American faunas. The fossil described as L. (Hoplolichas) hyleus 
Hall, from the Upper Helderberg group, known only from a portion of its cephalon, appears to 
be the nearest of any to this type of structure. 
CoNOLICHAS, Dames.—Frontal lobe highly elevated or conical. Occipital lobes conspicuous. 
Pygidium with two pairs of falcate spines and a broadly bispined terminal lobe. 
C. cornutus Clarke. Trenton. 
The L. (Conolichas) pustulosus Hall, of the Lower Helderberg, has a totally distinct 
form of pygidium, with but two pairs of broad lateral spines and a broad, undivided 
terminal lobe, like some of the forms of Homolichas, while the glabella with its 
elevated frontal lobe is unlike that of the latter subgenus and more similar to 
Conolichas, save in the absence of the occipital lobes. The composition of this 
species is peculiar and it will probably be found to stand as a distinct type of 
structure. L. (Conolichas) hispidus Hall, and L. (Conolichas) eriopis Hall, appear to 
be less like the normal Conolichas of the Silurian than the typical Arges of the 
Devonian. 
There are some American species which can not be placed with any of the 
foregoing divisions. Of these the one best known in all its parts is the D. halli 
Foerste (with which L. faberi Miller is synomymous), from the Hudson River group 
of Cincinnati, Ohio. This species is close in all structural features with L. margari- 
tifer Nieszkowski, from the Lyckholm beds of the Baltic provinces, or uppermost 
Lower Silurian; and for the latter Schmidt was unable to find a place among any of 
the subgenera adopted.by him. The head has a broad and not very convex frontal 
lobe, sharply isolated lateral lobes, distinct occipital lobes and prominent ocular 
nodes. The pygidium has two broad spines on each side, and a rounded terminal 
lobe divided by a short*and sharp median incision. 
Proretus PARviuscuLus Hall, 1866. 
Proetus parviusculus HALL, 1866. Adv. Sheets, Twentieth Rept., N. Y.State Cab. Nat. Hist., p.17. 
Proetus parviusculus HALL, 1872. Twenty-fourth Rept., N. Y. State Mus. Nat. Hist., p. 223, 
pl. vm, fig. 14. 
Proetus parviusculus HALL and WHITFIELD, 1875. Paleontology of Ohio, vol. ii, p, 109, pl. Iv, 
fig. 18. 
A few fragments, cranidia, free cheeks, and a single pygidium, of this species 
have been observed in rocks from the base of the Galena shales at St. Paul. Some 
of the glabellas, through compression, have the lobation more distinct than in the 
usual forms from Cincinnati; and in all, the granulation of the entire surface is a 
conspicuous feature. (Collection of Mr. Ulrich). 
