258 HISTORY OF BRITISH CRUSTACEA. 



Division ENTOMOSTRACA * 



Aquatic Crustacea covered with a shell of a horny or 

 leathery substance, formed of one or more pieces, in some 

 resembling a bivalve shell, in others a buckler which either 

 entirely or in part envelopes the body and the limbs of the 

 animal ; branchiae attached to the feet or jaws ; feet jointed 

 and fringed with hairs. They undergo a regular moulting 

 or change of shell, in some amounting to a species of trans- 

 formation. 



Legion BBANCHIOPODA. 



Mouth with organs adapted for mastication; branchiae 

 many, attached to the feet; body sometimes naked, but 

 most usually with a buckler-like envelope, in some enclosing 

 only the head and thorax, in others the whole body; feet 

 all bearing branchiae; antennae two or four, jointed, and 

 generally ciliated ; eyes sometimes two or three, but often 

 only one, or so close to each other as to appear single. The 

 species are all free, swimming at large in the water. 



* EvTOfjLos, an insect ; oarpaKov, a shell. 



