BRITISH 

 SESSILE-EYED CRUSTACEA. 



Order AMPHIPODA. 

 Group NORMALIA. 

 Division HYPERINA. 



IN this DIVISION the eyes are generally developed to 

 an abnormal size, often nearly occupying the whole 

 surface of the head. The antennae are frequently absent, 

 or, when present, more or less abnormal in their form, 

 rarely ending in a multiarticulate flagellum. The ap- 

 pendages of the mouth are rudimentary or obsolete. 

 The arms are small and less powerful than the walk- 

 ing legs, varying in different families from the simple 

 to the complexly-chelate form. The body has the 

 segments generally separate, although in some genera, 

 as Phrosina, of which we have no British example 

 recorded, the first two are fused together. The tail also 

 has the segments usually distinct, but in some exotic 

 genera, as Pronoe, Brachyscelus, &c., the fifth and sixth 

 segments are incorporated into one. The appendages 

 are more liable to aberration than in the Gammarida. 

 The animals are remarkable for the paucity of hairs that 

 exist upon their integumentary tissues, and are, for the 

 most part, parasitic in their habits, attaching themselves 

 to fishes or medusae ; they are able, however, to swim 

 with ease. 



VOL. II. B 



