234 NEW YORK STATE MUSEUM 
of them is a young individual. Among the fragments are some that 
prove that this inelegant squatty eurypterid attained to similar gigantic 
proportions as the associated Pterygotus. The material at hand permits 
us to give a fairly complete description of both the dorsal and ventral 
aspects and of the various appendages. 
Description. The outline of the body is a very broad oval, acute 
anteriorly and broadly rounded posteriorly, where a tubular tail (post- 
abdomen) of equal length is affixed, ending in a long, curved telson, of 
again half the length of the tail. | 
Cephalothorax. The cephalothorax is about as broad as long, its out- 
line is bluntly subtriangular, the two lateral margins converging at an 
angle of about 50° toward the anterior end which is truncated. The base 
is but little longer than the lateral margin (about one thirteenth). The 
anterior margin is about one third as long as the lateral margin. The pos- 
terior margin bends gently forward in the middle and is well rounded and 
projects slightly at the postlateral angles. The lateral margins were mod- 
erately convex; the frontal line slightly emarginate. There is evidence 
that the carapace was relatively convex along the middle axis and that it 
remained so to the anterior margin or even culminated there, where the 
compound eyes were borne on the sides of this frontal snoutlike promi- 
nence. The compound eyes are kidney-shaped, apparently smooth, without 
recognizable facets, about one tenth the length of the carapace and 
situated at the antelateral corners of the latter. The ocelli, well shown 
in one specimen, lie a little behind the center of the carapace [pl. 20], 
and probably occupied the apex of the head shield. The doublure is 
narrow at the sides; along the posterior margin it is 2 mm wide in medium 
sized specimens. 
Abdomen. The abdomen is broad and depressed in the anterior 
portion and narrow and tubular in the posterior portion, the two parts 
contrasting in a most striking manner. The dorsal side of the anterior 
preabdomen appears to have been entirely flat, but the middle third of 
the posterior part projects above the flat or slightly concave pleural portions 
