64 NEW YORK STATE MUSEUM 
there resembling a pendulum. Another, supposedly the male, appendage 
has been figured by Woodward [1869, p. 61] and by Laurie [1893, pl. 2, 
hg. 13]. This is hastate at its proximal end, and sharply pointed at its 
distal extremity in Woodward’s figure while Laurie represents it as a 
short, blunt process, but Laurie’s figure suggests that it was taken from 
a fragmentary specimen. Woodward and Laurie also figure the pair of 
triangular areas in front of the process. Schmidt mentions only faint traces 
of the sutures in P. osiliensis [op. cat. p. 78] and our material has 
not shown them at all. As they are also absent in Hughmilleria, they 
are probably a new acquisition in some species of Pterygotus. 
In Slimonia the appendages have retained fundamentally the same 
structure as in Pterygotus, but they show greater elaboration. The frontal 
2 
% 
Figure 2r Slimonia acuminata (Salter). Opercular appendages, 
(From Woodward) . 
paired triangular areas are distinctly set off. That form of the median 
lobe which is considered as belonging to the female [see Woodward, 1872, 
p. 116, fig. 35; Laurie, 1893, p. 513] terminates in three sharp points at 
its free end, while the other or male form terminates in a more or less 
truncated cone. This shows two or three deep transverse furrows, which 
Laurie thinks due to its having been eversible [op. czt. pl. 2, fig. 8]. 
In Eusarcus the genital appendages are still incompletely known. 
We have seen only fragments of the female appendage [pl. 33, fig. 3; 
text fig. 55] which exhibit the triangular areas, the hastate basal portion 
of the first lobe, and a faint impression of the second lobe. Indications 
of the interior tubular appendages have also been seen, According to 
this evidence the whole organ is a simpler expression of that in Eurypterus. 
