ON THE CARBONIFEROUS XIPHOSUROUS FAUNA. 149 
angle of the glabella, in a position homologous with their situation in Limulus. I venture then to 
give the opinion that the apparent differences between Prestwichia and Euprodéps, as stated by 
Messrs. Meek and Worthen, did not exist in nature, and that the genus Prestwichia was common 
to both Europe and North America during the Carboniferous Period. It is interesting in this 
connection to observe that the descendants of the Belinuride in Europe, survive in the Solenhofen 
Limuli until the Jurassic, and disappear during the Cretaceous period, not to arise again on the 
western coasts of the old world, while in North America, so far as the record shows, the type became 
extinct during the Mesozoic and Tertiary, to reappear in the Quaternary and present period. 
As regards the differences between Belinurus and Prestwichia, the former genusis the higher 
form, approximating Limulus in the consolidation of the eighth and ninth abdominal segments 
(forming the “abdomen” so regarded by Dr. Woodward) and in the very long caudal spine. In 
Prestwichia there is one abdominal segment less than in Belinurus, the short caudal spine forming 
the eighth. 
BELINURUS LACOEY Packard. PI. V, fig. 5. 
Belinurus lacoei Pack., Amer. Naturalist, xix, 292, March, 1885. 
Cephalic shield of the usual shape and length in proportion to the abdomen; the front margin 
as usual; the genal spine long, acute, extending obliquely outwards to a point parailel with one 
either a little behind the middle of the abdomen, or, in the older, larger specimens, nearly to a 
point parallel with the base of the caudal spine. The median lobe is, as usual, divided by the 
median line into two sublobes, so that the front edge of the entire lobe is indented in the middle; 
each sublobe contracts in width posteriorly behind the ocular or lateral angle bearing the com- 
pound eyes. The ocelli are not visible, but the compound eyes are partly- preserved; they are 
small, and of the usual kidney shape. The abdomen is much more-rounded than in the European 
B. regine, being twice as broad as long. It consists (including the caudal spine) of nine seg- 
ments. The median lobe is as broad at the end as at the base next to the thorax; there isa 
median tubercle on each segment, those on the third and last segment being larger than the 
others. The margin of the abdomen is broad and thin, giving rise to broad, acute, lateral spines. 
The caudal spine is very long and slender, a little swollen at the base; it is also triquetal, as in 
Limulus; it is nearly one-half longer than the body, i. ¢., longer than the whole body by the 
length of the head, and ending in a fine, slender, needle-like point. 
Length of the best preserved specimen 33™™ (including the caudal spine). 
Length of body, 15™™, 
Length of caudal spine, 18™™. 
Length of cephalic shield, 7™™; breadth at base of lateral spine, L6™™, 
Length of lateral spine, 4-5™™. 
Length of abdomen, 8™™; breadth (not including the spines), 12™™. 
In nodules at Mazon Creek, Illinois; Nos. 210"!, 210%, 210*, 212»; 2138, collection of Mr. Lacoe. 
While having the same number of abdominal segments, this species, the first representative 
of the genus which has occurred in America, differs from B. regine chiefly in the more rounded, 
less triangular outline of the abdomen, and in the smaller lateral abdominal spines. . It is prob- 
able that in Dr. Woodward’s figure of B. regine the compound eyes are not correctly placed. In 
our specimens of Belinurus they have the same relative situation as in Prestwichia dane and 
longispina. 
