LIMULUS AN ARACHNID. 53] 
Fic. 10 and 11.—Ventral and dorsal aspect of Galeodes sp. (from the 
object). 1 to vi. The cephalothoracic appendages. 7. Thoracic 
right tracheal aperture. /?, /°. Abdominal tracheal apertures. ge: 
Genital aperture. s¢. Sternal surface. a. Anus. cam. Camerostome. 
ct. Cephalothoracic tergite. 7¢'. Prothoracic portion of the cephalo- 
thoracic tergite. #. Separate mesothoracic tergite. 2, Separate 
metathoracic tergite. 
character of this portion of the sternal area, are the Spiders. 
In Mygale (M. avicularia) the coxe of the five hinder 
cephalothoracic pairs of appendages are arranged around a 
large oval sternite (fig. 9), which is divided into two portions, 
an anterior small prosternite (pro) and a larger mesosternite 
(mes). This double piece appears to correspond to the 
sternite of Limulus, marked pmsé in fig. 4, Pl. XXVIII. 
It is not a little remarkable that, in astructural feature 
observed in Limulus and zo# repeated in Scorpio nor in any 
Crustacean or Insect, the closest parallel should be found in 
another Arachnid; it is remarkable because it tends still 
further to determine the association of Limulus with the 
Arachnida in classification rather than with any other group. 
Behind the thoracic promesosternite of Limulus, separated 
from it by soft integument aud posterior to the coxz of the 
