exo 



cox 



Fig. 2. Schematic structure of (a) peropod and (b) uropod of a hyperiidean. 

 cox — coxal plate; 2 — 2nd article or basipodite; 3 — 3rd article or ishium; 4 — 4th article 

 or marus; 5 — ^5th article carpus; 6 — 6th article or propodus; 7 — 7th article or dactylus 

 (claw); bas — peduncle or basipodite; exo — outer ramus or expedite; end — inner ramus or 

 endopodite. 



spherical and shortened (family Platyscelidae); contrarily, sometimes it 

 has a long thin rostrum and constricted, elongated proximal part (Calam- 

 orhynchus, Oxycephalus, Leptocotis, Streetsia). The extreme develop- 

 ment of this tendency is observed in Rhabdosoma, in which the head 

 together with the rostrum is longer than the pereon and pleon together. 

 The head may be vertically conical, tapering downward from the top, 

 very high and short (family Phronimidae), very massive, exceeding the 

 pereon in length and height (family Cystisomatidae) or, contrarily, very 

 small, shorter and lower than pereon somite I (Lanceola, Megalanceola., 

 Mimonectes, females of Archaeoscina). The structure and size of the 

 eyes also vary greatly. They may occupy, as mentioned above, almost 

 the entire surface of the large spherical head (Hyperia and others, fam- 

 ily Paraphronimidae, Cyllopus) or only its dorsal part, or may be well 

 separated but joined with the small part of its lateral surface (Vibilia, 

 Bougisia). 



The eyes may undergo a more radical reduction. The receptor ele- 

 ments may disappear in them, in which case the eyes may acquire 



