GAMMAKIDES. 235 



AMPHIPODA . GAMMARIDES. 



NATATORIA. 



Subfamily GAMMARIDES. 



Body compressed. Eyes two, situated on a lobe between the 

 superior and inferior antennae. Inferior antennae not situated 

 posteriorly to the superior. Posterior pair of pleopoda folia- 

 ceous. 



The animals constituting this subfamily are generally 

 much compressed laterally. They bave two eyes, which 

 are situated on a lobe of the walls of the head, which 

 project anteriorly between the superior and inferior 

 antennae. The antennae are planted one above the other, 

 and are generally long, slender, and terminate in a fila- 

 mentary flagellum. The first two pairs of arms are 

 subchelate, and generally well developed. The posterior 

 pair of caudal appendages are generally leaf-like, and 

 fringed with cilia or hairs, but never stout spines or 

 hooks. The terminal tail-piece is generally squamiform, 

 except in one or two genera, where it appears to be 

 tubular or cylindrical, resembling a rudimentary seg- 

 ment. 



This subfamily must be considered as containing the 

 normal types of the order, the others being greater or 

 less departures from this perfect form. They are in- 

 variably aquatic animals, existing in fresh as well as 

 sea water ; and are most numerously distributed on our 

 shores. 



