I34 NEW YORK STATE MUSEUM 
round or tubular instead of flattened into a paddle; and the ninth segment 
forms a strong claw corresponding to the size of the whole leg. The legs 
form together a series that increases regularly in length backward, and 
the first four pairs are spinous. The carapace is large, the body slender 
and the telson distinctly styliform. | 
Laurie [1899, p. 582] has shown that his genus Drepanopterus differs‘ 
from Stylonurus only by a negative point of chief generic importance, 
namely, the fact that its last pair of appendages are not excessively 
elongated, and he states that Stylonurus developed from Eurypterus by 
way of forms most nearly represented by Drepanopterus, in which there 
was greater specialization of the fifth appendage, and reduction of the 
sixth appendage from the typical digging leg to a purely crawling one. 
The Otisville material and some of Laurie’s drawings indicate that in 
Stylonurus the second and third pairs of legs are also much elongated and 
specialized by the multiplication of the spines and by their development 
into broad lobes in species such as S. excelsior [see restoration plate 47]. 
The body has become still more slender and the slender form of the telson 
has given the genus its name. | 
Stylonurus alone of the whole branch has lived into the Devonic 
era, attaining there immense proportions. It represents an extreme of 
specialization that is strongly contrasted to that of the Pterygotus 
branch. 
The main stem represented by Eurypterus has persisted with little 
change into the Carbonic and even into the Permic. The prevailing ex- 
pression of Eurypterus in the Carbonic is, however, that represented by 
the subgenus Anthraconectes. We have elsewhere fully shown that the 
species referred to this group exhibit distinct phylogerontic characters in 
the excessive spinosity of the body due to the development of the ‘‘scales”’ 
into spines, in the elongation of the epimeral pieces and in the excessive 
length of the telson. 
A small independent branch that came off from Eurypterus is rep- 
resented by Eusarcus. In its triangular carapace, anterior eyes, broadly 
