Foerste.] 
268 
[May lj 
the Ohio forms have been found at Hanover, Indiana. The one best 
preserved is 19 mm. long and 22 mm. broad, across the palpebral 
lobes. 
We have seen specimens from the Niagara of New York, usually 
referred to Illaenus barriensis or Ioxus which we cannot distinguish 
from the forms described by us under Illaenus ambiguus. This form 
is so similar to Illaenus msignis , Hall, that it may prove to be not 
a distinct species. 
Illaenus Daytoyiensis , Hall and Whitfield, does not seem to occur 
in the Clinton outside of Ohio, and probably Indiana, although it 
occurs at a somewhat higher horizon farther westward. Figs. 9, c, 
d , of PI. A, 66, Pal. N. Y., Vol. n, belong to this second and dis- 
tinct species. 
Illaenus Ioxus, Hall. 
(plate hi, FIG. 20.) 
This species is figured from the Clinton of New York under Figs. 
9, a, 6, PL A. 66, Pal., N. Y., Vol. n ; and also from the Niag- 
ara of that State. 
A very unsatisfactory fragment of a glabella, not presenting the 
strong dorsal furrows of Illaenus Daytonensis nor the narrow 
curved dorsal furrow terminating in a pit of Illaenus ambiguus , 
but apparently having the long palpebral lobes of Illaenus Ioxus , is 
placed here as a last resort. The figure of this specimen will ex- 
plain our hesitation. A large pygidium found here shows affinities, 
rather with Illaenus Daytonensis. Outside of New York and this 
doubtful locality, the species is not known to occur in the Clinton 
Group, but occurs in Wisconsin. 
The specimens from the Niagara of Waldron, Indiana, identified 
with this species, do not clearly belong here. 
Phacops pulchellus, Foerste. 
(PLATE IV, FIGS. 20, 21.) 
Specimens of the following description were found at Cumberland 
Gap, Tennessee. Glabella strongly divided from the occipital 
ring by the occipital furrow, which is deepest laterally, leaving a 
short, narrow, strongly convex connection between the occipital 
ring and the glabella. Glabella moderately convex above, strongly 
convex at its contours. Dorsal grooves narrow but very distinct, of 
fair depth, straight, forming angles of about fifty degrees with one 
