260 HISTORY OF BRITISH CRUSTACEA. 



The Apus swims on its back as easily as on its lower sur- 

 face, using the feet, which are constantly in motion. Its 

 food seems to be chieflv the smaller kinds of Eyitomostraca , 

 the shells of which they can readily break with their man- 

 dibles. Their eggs retain their vitality for a great while ; 

 as the little creatures have been known to appear in a ditch 

 that was suddenly filled with water after having been dried 

 up for two or three years. 



Gen. 136. APUS, Scopoli. 



Plate XV. fig. 1 a, shows the head viewed in front. 



Apus cancriformis, Schrfer. Shield-Shrimp. « (Plate 

 XV. fig. 1.) — Brownish-yellow, clouded with darker colour; 

 shield covering more than half the body, ovate. 



Hab. Pond on Bexley Common. Devonshire, Bristol. 

 (Baird, 1. c. p. 31.) 



Fam. NEBAL1ABM, Lead. 



Antennse two pairs, large and branched ; eyes two, pe- 

 dunculated ; twelve pairs of feet, eight for breathing, and 

 four for swimming. Carapace large, enclosing the head, 

 thorax, and part of the abdomen, as if in a bivalve shell. 



