THE EURYPTERIDA OF NEW YORK 123 
entiation of the abdomen and the smaller size of the telson. In these 
palingenetic characters the nepionic stage resembles so much the Cam- 
bric Strabops, that we shall designate this as the Strabops stage. We 
shall use these characters in the reconstruction of the primitive ancestor 
of the eurypterids in the next chapter and the discussion of their taxo- 
nomic position. 
In reference to this taxonomic position it may be stated here that 
the ontogeny of the eurypterids fully corresponds to that of Limulus in 
lacking any indication of a nauplius or zoea stage; that the larvae of the 
eurypterids (nepionic stage) have in common with that of Limulus: 
1 The large size of the carapace 
2 The broad border of the latter (in Stylonurus myops) 
3 The prominent cardiac region of the carapace, giving it a 
trilobate character (in Stylonurus myops, Eusar- 
cus (?) cicerops, Pterygotus globiceps) 
4 The lack of differentiation of the abdominal segments 
5 The undeveloped telson. 
They differ from it in: 
1 The terete abdomen ; 
2 Megaloptic development of the lateral eyes, and 
3: Their nearer approach to the margin 
4 Having but nine abdominal segments, while Limulus is hatched 
with the full number of segments. 
The meaning of these agreements and differences in the development 
of the eurypterids is discussed more advantageously in the chapter on the 
taxonomic relations of the eurypterids where also the ontogeny of the 
eurypterids is compared with that of the scorpion. 
