206 PALEOZOIC PALEONTOLOGY. 
being about one-half the distance between their outer extremities 
measured in a straight line. The second pair are longer, parallel 
for about one-half their length with the first pair, then directed 
more strongly backward. The third pair are longer than the second, 
subparallel with them, but deflected abruptly backward at their ex- 
tremities, where they are widened into a slight pit or excavation, not 
reaching the occipital furrow. The occipital segment is widest in 
the middle. The cheeks are but imperfectly preserved. The entire 
surface of the glabella is covered with low, distinct, scattered tubercles. 
The dimensions are: length of glabella, 12.5 mm.; length of 
glabella and occipital segment, 14.5 mm.; width of glabella, 13.5 mm. 
Remarks.—This species was originally described from the Middle 
Trenton limestone at Trenton Falls, New York. In New Jersey the 
species has been observed only in the Black River horizon of the 
formation, where it is associated with Leperditia fabulites and Dal- 
manella subequata. Cheirurus vulcanus Bill.,* described from the 
“Quebec group,” Cow Head, Newfoundland, and from Stanbridge, is 
a very similar species. It is possible that the two are identical, in 
which case the specific name, vulcanus, has priority. 
PTERYGOMETOPUS CALLICEPHALUS (Hall). 
Plate XV., Figs. 29-32. 
1841. Phacops callicephalus Hall, Pal. N. Y., vol. I., p. 247, pl. 65, 
figs. 3 a—t. 
189%. Pterygometopus callicephalus Clarke, Pal. Minn., pt. IL., p. 
731, figs. 51-52. 
Description.—Head sublunate in outline, obtusely subangular in 
front, genal angles broad and rounded, with no indication of spinules. 
Glabella large, depressed-convex, broad and rounded in front, be- 
coming much narrower behind; frontal lobe large, subelliptical in 
outline; anterior pair of glabellar furrows starting from opposite the 
anterior extremities of the eyes, directed obliquely backward and each 
one extending over a little more than one-third the width of the 
glabella; second pair of glabellar furrows shorter and a little shal- 
* Pal. Foss., vol. I., p. 284, fig. 271; p. 324, fig. 310. 
a 
