170 BRITISH COPEPODA. 
female P. viride, the very poorly developed or almost 
obsolete fourth body-segment being probably a mark 
of immaturity. Itmust be admitted, however, that the 
size 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. subrotundwm, and the caudal 
lamine, as well as the antenna, are almost identical 
with those of the female vide. 
Sub-family 9. Ipyinam, nov. sub-fam. 
Cephalothorax more or less depressed. Anterior 
antenne 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 Jdya and Scutellidiwn, 
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, 
