GENERAL CHARACTERS. 5 



of a peduncle consisting of three joints, and a terminal 

 multiarticulate filament, supplied with auditory cilia. Oc- 

 casionally there is a second appendage, generally rudimen- 

 tary, but in some of the Phoxides it is of almost equal 

 importance to the primary filament ; the secondary ap- 

 pendage is, however, never furnished with auditory cilia. 



The posterior or inferior pair of antennae (c) consists 

 of a peduncle of five joints and a multiarticulate fila- 

 ment. The first two joints are closely incorporated, and 

 bear an olfactory denticle ; but sometimes, as in Talitrus, 

 the denticle is wanting, probably from the peculiarity of 

 its condition of existence, as the Talitri do not live in 

 water. Occasionally the terminal filament has the joints 

 fused together. This numerical decrease is invariably 

 attended with an increase of strength. 



In some genera of the Hyperina both pairs of antennae 

 assume a rudimentary condition to such an extent that 

 their respective parts cannot be readily defined : some- 

 times even one or both may be absent. 



The jaws or mandibles (d) are placed between an 

 anterior and posterior lip or labium ; they consist of a 

 pair of curved triangular blades, each furnished with a 

 cutting edge and a grinding tubercle. Within the inci- 

 sive margin there is frequently a second movable plate, 

 formed upon the type of the preceding. Each mandible 

 has very generally, though not universally, an articulated 

 palpus or appendage. The anterior pair of maxillae (e) 

 consist of three or four foliaceous plates, whereas the 

 second pair (/) have but two ; they are extremely deli- 

 cate, and furnished, upon their anterior margins, with 

 plumose hairs, some of which are strengthened into 

 spines of various shapes. Exceptions to the normal 

 forms exist in the Hyperina. 



The foot-jaws, or pedipalps (siagonopoda, I. O. W., or 

 maxillipedes) (g) t are the posterior pair of appendages 



