280 
BRITISH ENTOMOSTRACA. 
Genus 4 — Trebhjs, 
Trebius, Kroyer , Tidsskrift. 
— M. Edwards , Hist. Nat. Crust. 
— Thompson, Ann. and Mag. Nat. Hist. 
Character . — Fourth pair of feet slender, and divided 
into two branches, adapted for swimming. Thorax pos- 
sessed of three distinct articulations. Frontal plates 
destitute of small sucking-discs or lunules. 
1. Trebius caudatus. Tab. XXXIII, figs. 3, 4. 
Trebitjs caudatus, Kroyer , Tidsskrift, ii, 30, t. 1, f. 4. 
— M. Edwards, Hist. Nat. Crust., iii, 458. 
— Thompson , Ann. and Mag. Nat. Hist., xx, 248. 
Description. — Demote. Carapace nearly oval, rather 
longer than broad. Frontal plates of considerable size. 
Antennae well developed ; setae on external edge of basal 
joint plumose. 
Thorax narrow on first two joints, especially on second ; 
last nearly quadrilateral, a little narrower at upper extre- 
mity than lower, which is nearly straight on the edge. 
Abdomen long and narrow, nearly as long as the thorax, 
slightly narrowed towards the centre, and terminated by 
two small caudal appendages, which give off three long and 
one short plumose setse. Sternal fork with simple branches. 
First pair of foot-jaws larger than in any of the Caligi, 
and strongly hooked at their apex. Third pair much 
smaller. Fourth pair of feet short, with basal joint broad, 
and the two terminating articulations short, oval, and fur- 
nished with several rather stout setse. Oviferous tubes 
short, and rather broad. 
Male. The male is much smaller than the female. Cara- 
pace broader. 
Thorax, two first segments of much the same form as 
in the female ; last joint somewhat hexagonal. 
