62 NEW YORK STATE MUSEUM 
of Limulus than to that of Thelyphonus, we must not forget that Holm 
has found important corroborative evidence for his sex determination of 
the male in the clasping organs of the second endognathites. 
Accepting the determinations of Woodward, Schmidt and Holm, the 
female appendage consists of two single lobes and two paired terminal 
Gen. duct. Ut. Mase. Gen. duct. 
Figure 18 Diagram to indicate the 
probable nature of the mesoso- 
matic segments of Eurypterus. 
Ut. masc., Uterus masculinus; 
gen. duct, genital ducts. (From 
Gaskell) 
Figure 19 Eurypterus fischeri Eich- 
| wald. Female genital appendage of oper- 
Figure 20 Eurypterus lacustris culum. At the right the tubular append- 
Harlan. Specimen showing the age. (From Holm) 
paired genital appendages turned 
to one side. Natural size 
pieces.' The first of the single lobes is the largest; it is pointed in front, 
where it extends between the pentagonal basal pieces, with which it is 
connected by sutures. The middle portion is found occupying the space 
between the lateral opercular plates which here do not meet in the median 
— 
1 Holm also counts the two pentagonal anterior areas [ see above] as belonging 
to the genital appendage. 
