THE EURYPTERIDA OF NEW YORK 43 
the limbs of Limulus and theeurypterids that are among the strongest proofs 
of their intimate relationship. 
The six pairs of limbs are currently divided into the preoral (the first) 
and postoral (the following five pairs). The preoral limbs are the chelicerae 
or mandzbles, the postoral the walking, 
and burrowing or swimming legs. Be- 
sides these the mouth is surrounded 
by platelike appendages, functioning as 
lips. These are the epzstoma, endostoma 
and metastoma. — 
a The chelicerae in Limulus are 
small [see text fig. 10] and consist of 
three segments, the much compressed 
but relatively long basal segment and 
the two forming the pincers or chelae. 
The basal joint articulates, as Holm 
has pointed out, with an unpaired, 
lanceolate plate placed between the 
coxal segments of the first pair of walk- 
ing legs. 
The preoral appendages of the 
eurypterids exhibit great differentia- 
tion. They are smallest in Eurypterus, 
where they have been described in 
detail by Holm and have proved to 
have almost the exact structure of 
those in Limulus. We figure here the 
chelicerae of E. remipes and E. 
lacustris [plate 7, figure 1, and 
ee Ra 
a AN 
2 
'3—SPp 
Figure ro Limulus polyphemus; female, 
from ventral surface 
ab, abdomen; am, anus; ch, chelicera; cht, chi- 
larium; cp, cephalothorax; ol, olfactory 
organ; op, operculum; sp, spine. (From 
McMurrich) ) 
plate 12, figure 1] which verify Holm’s observations. Those of Stylonurus 
have a like structure and similar relative size as shown by Hall and Clarke 
[seeunder S. excelsior]. Eusarcus had similar chelicerae which, how- 
