THE KIMMSWICK AND PLATTIN LIMESTONES 
217 
dorsal furrow and from the furrow following the posterior out- 
line of the fixed cheeks. The ocular ridge is either faint or obso- 
lete; when present, it starts off from the vicinity of the first 
pair of glabellar furrows. The pustules tend to be more con- 
spicuous anteriorly and also along two diverging lines which 
extend from near the neck furrow forward toward the frontal 
lobe in such a manner as to leave a median area in which the 
pustules are less prominent. The pustules are less prominent 
also between the two rows of more prominent pustules and the 
lateral glabellar lobes. On the largest cranidium, 14 mm. long, 
the most prominent pustules attain a height of 0.5 mm. None 
are developed into spines. The fixed cheeks are indented with 
pits, and between these there are a few granules of which several 
tend to be prominent. 
Found at locality 2 along Sanders branch, in the Kimmswick 
limestone. 
From typical Ceraurus hispinosus Raymond and Barton (plate 
II, fig. 23 of this Bulletin), from the Black River formation of 
the Ottawa area in Canada, the Ralls County specimens differ 
chiefly in the absence of any pustules sufficiently strong to sug- 
gest the presence of spines. From Ceraurus dentatus Raymond 
and Barton, from the Trenton formation of Ontario and New 
York, they differ in having more rotund glabellar lobes. 
37. Ceraurus plattinensis sp. nov. 
Plate XXI, figs, 18 A, B; plate XXIII, figs. 3 A, B 
Cephalon relatively short. The continuation of the occipital 
furrow along the posterior part of the fixed cheeks is nearly 
straight as far as the genal angle ; in consequence the angle 
between the posterior margin of the cephalon and the genal 
spines appears more abrupt. In other respects the backward 
curvature of the genal spines resembles that of Ceraurus den- 
tatus, The lateral lobes of the glabella are small and rotund, 
while those of Ceraurus dentatus are more nearly transversely 
oblong. The eyes are set far back, almost opposite the second 
pair of lateral lobes or slightly farther forward. A faint ocular 
