THALESTRIS. 12] 
claw, and bearing three or more setiferous marginal 
lobes. Second pair forming a strong prehensile hand. 
Both branches of the first pair of feet form strong pre- 
hensile organs with terminal claws, and are 3-jointed ; 
first joint of the inner branch much elongated, second 
and third very short; first and third joints of the 
outer branch short, the middle joints greatly elongated. 
The second, third, and fourth pairs have both branches 
3-jointed, and adapted for swimming, except in the 
second pair of the male, where the inner branch has 
the third joint wanting or very much reduced in size, 
and converted into two or three strong spines. Fifth 
pair of feet 2-branched, foliaceous; both branches 
in the male usually much reduced in size, the inner 
often almost obsolete. Ovisac single. 
1. Tatesrris mysis, Claus. Pl. LVIII, figs. 1—13. 
Thalestris mysis, Claus. Die frei lebenden Copepoden, p. 130, 
t. xviii, figs. 12—16 (1863). 
— — Boeck. Oversigt Norges Copepoder, p. 44 (1864). 
Body elongated, slender; abdomen very long, the 
first two segments much longer than the rest; ros- 
trum of moderate size, sharp and slender. Anterior 
antenne (fig. 2) 9-jointed; the first four subequal 
and considerably longer than the following joints. 
Inner branch of the second pair of antennz 2-jointed 
(fig. 4), armed with stout sete. Mandible-palp well 
developed and strongly setose (fig. 5); maxilla also 
