BRITISH 
SESSILE-EYED CRUSTACEA. 
Order—AMPHIPODA. 
Group—NORMALIA. 
Division—HY PERINA. 
In this Diviston the eyes are generally developed to 
an abnormal size, often nearly occupying the whole 
surface of the head. ‘The antenne 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 Pronoé, Brachyscelus, &c., the fifth and sixth 
segments are incorporated into one. The appendages 
are more liable to aberration than in the Gammaride. 
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 meduse; they are able, however, to swim 
with ease. 
VOL. U1. B 
