ON THE CARBONIFEROUS XIPHOSUROUS FAUNA. 147 
from the others in ending abruptly, the penultimate joint being long and of the same width 
throughout, and truncate at the distal end, where it gives rise to three small, sharp spines; there 
are also traces of a terminal minute joint from which two spines arise, 
Length of second, third, fourth, and fifth pairs of legs, 16™™, 
Length of sixth pair, 17™™, 
Length of penultimate joint, 6™™, 
Thickness, 1™™, 
The legs are nearly identical in shape and length with those of the larva of Limulus described 
and figured in my Development of Limulus (PI. 1, figs. 24°, 25%, and 234), though perhaps a little 
shorter, as they do not reach beyond the edge of the cephalic shield. It thus appears that in 
respect to its limbs as well as the shape and proportions of the body the Prestwichia resembles 
the larval Limulus. Thus Limulus in its development passes through a trilobitic, and afterwards 
a Belinurid stage. 
PRESTWICHIA LONGISPINA Packard. PI. V, fig. 4. 
Euprodps longispina Pack., Amer. Naturalist, xix, 292. March, 1885. 
The specimen upon which this species is founded is Mr. Lacoe’s Nos. 215*» (impression and 
reverse), and was probably a molted skin (PI.-V, fig. 4). The body is considerably distorted by 
pressure, but the specific distinctness from P. dane is marked. The species will he readily dis- 
tinguished by the very long genal spines; they extend nearly or quite to a point opposite the base 
of the caudal spine. The abdomen appears to be narrower in proportion to the cephalic shield 
than in P. dane while the genal spines are longer and narrower. The caudal spine is not well 
preserved. 
Length of body (not including the caudal spine), 20™™, 
Length of head, 10™™, 
Length of abdomen, 10™™, 
Breadth of cephalic shield, 24™™, 
Breadth of abdomen, 13™™. 
Length of lateral cephalic spine, 13™™. 
Pittston, Pa., Butler mine, Nos. 215%», collection of Mr. Lacoe. 
In another larger specimen (Lacoe’s No. 214, Pl. VI, fig. 3), the glabella, with the eyes, ocelli, 
and a part of the left lateral spine are preserved. Whether this is the same species as P. longispina 
I cannot tell with certainty, as the genal spines are not sufficiently well preserved, but provision- 
ally it may be regarded as belonging to the species under consideration. The median lobe of the 
head is larger in proportion to the entire cephalic shield than in P. danw, and the eyes are nearer 
the lateral margin. The ocelli are situated on the median ridge of the lobe, somewhat behind the 
indentation between the lobes. The individual is without doubt a Prestwichia having the same 
number of abdominal segments as in P. dane. 
Length of body (without the caudal spine), 30™™, 
Breadth of cephalic shield (estimated), 37™™. 
Length of cephalic shield, 17-18"™™. 
Length of abdomen, 13™™, 
Breadth, 23™™, 
Estimated length of lateral cephalic spine, 15™™, 
Distance between the compound eyes, 17™™. 
Distance from ocelli to the front edge of body, 6™™. 
Distance from ocelli to hinder edge, 21™™. 
Oakwood Colliery, Wilkes Barre, Penn., collection of Mr. Lacoe, No, 214°. 
Regarding the position of the Illinois and Pennsylvania beds containing these fossils, Mr. Lacoe 
writes me: “The horizon of the Pennsylvania specimens of Euprodps is much higher than that of 
Mazon Creek. The latter is at the very base of the productive coal-measures in shale over the 
bottom seam of coal. The specimen from the Butler mine, Pittston, is from shale over coal ‘ H’ 
(Mammoth vein), at the top of the lower productive coal-measures, about 300 feet above, and that 
from the Oakwood colliery is either from the same horizon or the bottom of the lower barren 
