TRILOBITES. 728} 
Bathyurus spiniger.] 
Baruyurus spinieER Hall, (sp.), 1847. 
Acidaspis spiniger HALL, 1847. Palaeontology New York, vol. i, p. 24, pl. 64, fig. 5. 
With the aid of a series of specimens from High Bridge, Kentucky, and Dunleith, 
Illinois, it has been possible to complete in a measure our knowledge of this species. 
The original was an imperfect cranidium showing a closely tubercled, ovoid glabella 
slightly broadest anteriorly, and a wide occipital ring produced axially into a spine. 
Vig. 38.—Cranidium of Bathyurus spiniger Hall. 
The specimens in hand have the same characters, and the following additional 
features may be indicated. In spite of the coarse and closely set tubercles, covering 
the upper surface of the glabella, two pairs of lateral grooves are discernible. Both 
are short, the first being transverse, the second directed backward. The glabellar 
lobes are all indistinct, the frontal lobe covering fully one-half of the glabella. The 
frontal border is narrow, but broader than in B. extans, concave about the glabella, 
and turned up at the edge. The palpebral lobes are moderately large, approximate 
and posterior. The occipital ring is tubercled and its central spine about one-third 
the length of the glabella. 
Associated with these cranidia, in both the localities mentioned, are pygidia, 
entire on the margin, and having the general form of B. extans, but more highly 
convex, the lateral slopes being quite abrupt. The axis extends to the narrow, 
gently concave margin where it ends abruptly. It bears three distinct annulations, 
with traces of a fourth and fifth. The first of these has a small median, spinous 
tubercle; on the second the tubercle is not so large; on the third it is again more 
conspicuous. Close behind this lies the base of a strong, erect or slightly recurved 
spine, and with it, in some of the specimens, the spinule on the third annulation is 
merged, There is also a row of small tubercles on each side of the axis. The pleure 
ys 
Hf. 
bear four flat ribs, the first of which is grooved. - 
Figs. 39, 40.—Pygidium of Bathyurus spiniger Hall; with outline profile showing the probable size 
of axial spine. 
Formation and locality.—The original specimen of this species was said to be from “the central 
part of the Trenton limestone in the Mohawk valley, and ina similar position near Montreal.” The 
horizon of the specimens from Dunleith, Ill., is essentially equivalent to this, though those from High 
Bridge, Kentucky, are said by Mr. Ulrich (by whom both have been loaned), to be from the upper part of 
the Birdseye beds. 
