DOEOPYGUS. 133 



jointed, setae naked or finely plumose ; fifth pair small, 



1- jointed. Inhabiting the branchial sac of various 

 simple Ascidians. 



1. DOEOPYGUS PULEX, Thorell. PL XXVIII, figs. 



112. 



Doropygus pulex, Thorell. Loc. cit., p. 46, tab. vi, fig. 8 (1859.) 



Adult female. Cephalothorax produced into a 

 short, blunt, triangular rostrum, third and fourth 

 thoracic segments united to form the ovarian envelope. 

 Abdomen much narrower than the cephalothorax 

 (fig. 1), and bent upon it so as to form almost a right 

 angle. Fifth abdominal segment longer than the 

 fourth (figs. 11, 12), partially furcate, and divided 

 into two subtriangular segments. Caudal segments 

 very long and slender, transversely divided near the 

 middle, curved and divergent, and bearing three or 

 four minute apical setae. Anterior antennae 10- 

 jointed, the two basal joints about once and a half 

 the width of the third joint, the third, fourth, fifth, 

 and sixth progressively decreasing in width, the last 

 four subequal as to width, the sixth joint longer than 

 any except the first. The whole limb is densely beset 

 with long hairs on the external margin and apex, and 

 the second joint has also two conspicuous tooth- 

 like spines. The posterior antenna (in the adult) 

 has the claw longer than the second joint (fig. 5, 

 PL XXVIII, is taken from an immature specimen, and 



