300 
HISTORY OF BRITISH CRUSTACEA. 
in Berwick Bay. He describes its motion as very peculiar ; 
it generally swims on its back, and instead of darting for- 
ward through the water, like the other species of the family, 
it springs with a bound from the bottom of the vessel, 
where it remains when undisturbed, up to the surface of 
the water. It effects this by curling its body into a ball, 
and then suddenly assuming a straight position. 
Alteutha depressa, Baird.— Body depressed, flat, broad; 
eye of a fine ruby colour. 
Hab. Berwick Bay. 
Fam. II. DIAPTOMIDM , Baird. 
Head generally distinguishable from the body, though 
firmly articulated with first ring of thorax. Three pairs of 
well-developed foot-jaws. Five pairs of legs, last pair of 
different structure from the others, and differing from each 
other in the two sexes. One eye. In the male, one of the 
antennae alone is furnished with a swollen hinge-joint, with 
which he seizes and holds the female. 
Gen. 164. DIAPTOMUS, Westwood . 
Head distinguishable from the thorax; thorax and ab- 
