194 PALEOZOIC PALEONTOLOGY. 
between the furrows are broad and flat. The axis is apparently un- 
segmented, though this cannot be stated with certainty, because of — 
the imperfect condition of the specimen. 
BUMASTUS TRENTONENSIS (Emm.). 
Plate XIV., Figs. 8-13. 
1842. IJllenus trentonensis Emm., Geol. N. Y., Rep. on 2d Dist., 
[Oppo e slo ash \ 
1897. Bumastus trentonensis Clarke, Pal. Minn., pt. IL, p. 718, 
figs. 30-35. 
Description.—Head strongly convex, subsemi-circular in outline, 
not trilobate, and with no prominences save the eyes, which are located 
posteriorly, well toward the lateral margins. A pair of longitudinally 
elongate, sublunate depressions are situated on a transverse line join- 
ing the eyes, about half way between the eyes and the median lne 
of the head. These depressions are slight or almost obsolete upon the 
exterior of the test, being much more strongly marked upon the casts. 
Aside from these depressions and a few fine lines near the anterior 
margin and running parallel with it, the test of the head is perfectly 
smooth. The pygidium is smooth throughout, not trilobate, resem- 
bling the head in size and general outline. Nine thoracic segments 
are present in the only specimen observed in which they are preserved. 
The dimensions of a rather small specimen are: total length of 
body, 20 mm.; breadth, 10 mm.; length of head, 8 mm.; length of 
thorax, 6 mm.; length of pygidium, 6 mm. 
Remarks.—This species is one of the commonest trilobites in the 
Trenton limestone of New Jersey, and occurs at nearly all horizons 
from which fossils have been secured. It is associated with Leperditia 
fabulites in the Black River horizon of the formation at Jacksonburg, 
and continues to occur in most of the beds nearly to the top of the 
same section. The species exhibits considerable variation in size, the 
largest heads attaining a length of 16 mm., though the usual size is 
about 9 or 10 mm. The large specimens have some resemblance to 
B. orbicaudatus Bill., but are more convex. 
