THE EURYPTERIDA OF NEW YORK 157 
of preoral chelicerae in place of antennae, already inferred by Schmidt, 
was demonstrated,’ [see restoration pl. 3, fig. 1]. The fifth segment of the 
second endognathite in the male carries a long, curved, tubular pro- 
cess [text fig. 32] which, by analogy with Limulus, Holm considered 
as a clasping organ employed during copulation. The epicoxite of the 
coxal segments before observed by Laurie in Slimonia and Ptery- 
gotus, was found in its proper position in Eurypterus and a circular 
perforation with very thin covering membrane has been observed close 
to the inner margin of the coxa of the fourth endognathite [see text 
fig. 12; pl. 7, fig. 6]. A corresponding organ in the living Limulus 
polyphemus was discovered by Holm on 
the coxae of the third and fourth endognathites 
near the epicoxite. On account of the structure 
of this organ and its position on that side of the 
coxa which is turned toward the outside, it was 
suggested that it has an auditory function. This Pigure 32, Second enna 
structure has also been observed by Sarle in with clasping organ of male, 
; ; the long reflexed hornlike 
Hughmilleria socialis [pl. 62, fig. 5] appendage of underside. 
. . . . (From Holm) 
and by the writers in E. remipes [pl. 7, fig. 6]. 
A new organ was discovered, the endostoma. This consists of a small, thin, 
deeply emarginate shield, not clearly bounded on the sides, which formed 
the inner posterior margin of the mouth [text fig. 13].’ Further, the con- 
nection of the metastoma with the ventral integument of the cephalothorax 
by a doublure [text fig. 14] was shown. The distinction between male and 
female genital appendages was clearly elaborated and the presence demon- 
strated of an interior paired, curved, tubular organ connected with the 
1Eurypterus scorpioides, in which the chelicerae had been found before 
by Laurie, is in our. view generically distinct and an Eusarcus although on the strength 
of the presence of equal chelicerae in both, Holm argues for their eongeneric character. 
?We describe and figure here the endostoma of Pterygotus, hitherto unobserved 
[pl. 7x, fig. 3]. 
