170 BRITISH COPEPODA. 



female P. viride, the very poorly developed or almost 

 obsolete fourth body-segment being probably a mark 

 of immaturity. It must be admitted, however, that the 

 siae of the animal fully equal to that of P. viride 

 is an argument against this view. But I have seen no 

 male referable to P. subrotundum, and the caudal 

 laminae, as well as the antennae, are almost identical 

 with those of the female viride. 



Sub-family 9. IDYIN^J, nov. sub-fam. 



Cephalothorax more or less depressed. Anterior 

 antennge 7 9- jointed ; inner branch of the posterior 

 pair 1 4-jointed. Mandible-palp well developed, 

 2-branched, or provided with complex setiferous plates. 

 Both pairs of foot-jaws forming elongated clawed 

 hands. Inner branch of first pair of feet 2-, outer 

 3 -jointed; three following pairs having both branches 

 3-jointed; fifth pair elongated, 2-jointed. One ovisac. 



This group includes only Idya and Scutellidium, 

 which are very like each other in habit and general 

 appearance. The structure of the mandible-palp is, 

 however, widely different in the two genera, and might 

 probably be safely used as the basis of separation into 

 two sub-families. 



