THE EURYPTERIDA OF NEW YORK 339 
either side. Its distal end is reentrant and fused to the posterior part. 
This part is a little narrower, slightly tapering and beveled in from either 
side*for one fourth the breadth, to the sides of a slightly raised platform 
which is flat-topped for the greater part of its length, but becomes concave 
posteriorly, forming a shallow groove at the abrupt end. The terminal 
angles are noticeably truncated. The appendage carried by the second 
sternite is partially covered by that of the operculum. It is very slender, 
its greatest breadth not exceeding one sixth the length. The anterior 
half is sublanceolate with a triangular base; the posterior is attenuate and 
terminates just within the end of the cleft. In the male the appendage 
is simpler and confined to the operculum, the following sternite being 
entire. It is wider and somewhat shorter than that of the female, the 
average length being only ahout two and one half times the breadth. 
It is convex, broadly lanceolate and slightly produced at the posterior 
free end which just clears the edge of the operculum. A specimen in 
which a portion of this organ is scaled away gives a cast of the interior 
showing small elevated lines radiating from near the center backward, 
and may possibly represent part of the vascular, or duct system of this 
organ. The two sexes are about equally represented in numbers. 
The whole surface of the body is covered with imbricating, crescent- 
like or angular scales, sometimes carrying smaller ones of the same pattern. 
These scales are so minute On certain areas as to appear almost obsolete. 
They are most conspicuous on the ventral side of the preabdomen and 
appendages. On the cephalothorax and abdomen the scales point back- 
ward, on the paired appendages toward the distal end, and on the epistoma, 
forward. : 
This singular creature has the appearance of an Eurypterus with 
the carapace of a Pterygotus. The Pterygotuslike aspect of the carapace 
is principally due to the marginal position of the compound eyes. 
Another character worthy of mention is the ornamentation,! which 
consists of flat, imbricating scales that are crescentlike near the anterior 
margin and become angular posteriorly. They are evenly distributed over 
the entire body, carapace [pl. 60, figs. 6, 8], endognathites, metastoma, 
operculum and its appendages, save the telson where they have not been 
observed. On the distal segments of the endognathites they appear as. 
small tubercles. : 
‘It is drawn too coarse on the original figures here reproduced and would hardly 
be noticeable in natural size drawings. ; 
