CRUSTACEA, 





and a long mnltiarticulate flagellum, which, however, may bo more or 

 less rudimentary. The anterior antennae, which are always longer 

 in the male, often bear a short accessory flagellum and present 

 numerous modifications in their special form. In the Hyperina they 

 are very short in the female ; while in the male they are of consider- 

 able length and are closely beset with olfactory hairs. The posterior 

 antenna? are frequently longer than the anterior : in the male 

 Typhidce they are folded in a zigzag fashion, and in the Corophiidce 



I* v 



a, 857. TJironima sedentaria, a, female; J, male. O, eyes; A', A", the two prnrs of fin 

 tennse ; Kf, jaws ; D, intestine ; JET, heart and aorta ; K, gills ; Ov, ovary ; -A", nervous 

 system ; Dr, glands in the chela of the fifth pair of legs ; G, genital opening. 



are modified to form strong pediform appendages. In the female, on 

 the contrary, they may be degenerated and represented only by the 

 basal joint (Phronima) (fig. 357, a and b). 



The mandibles are powerful biting plates with a sharp, usually 

 toothed edge and a lower masticating process. They usually possess a 

 three-jointed palp, which is occasionally reduced. The anterior bi- 



