17 , 6 
Chilton: A New Amphipod 
519 
The third perseopod is about the same length as the first and 
second, the basal joint is oval but the posterior margin is not 
greatly produced ; it bears a number of fine setae in small inden- 
tations; the carpus and propod are subequal and shorter than 
the merus. 
The fourth peraeopod is similar in shape and structure to the 
third but is longer, being intermediate in length between the 
third and fifth peraeopods. 
The fifth peraeopod is much longer than the third and fourth 
but similar as regards the shape of the basal joint; the carpus 
and propod, however, are considerably longer in proportion to 
the merus, all three joints being slightly widened, their margins 
bearing stout setules arising from slight serrations; the finger 
is small and acute. 
The pleopods are all well developed, the branches in each being 
equal in length and many-jointed. 
The first and second uropods extend backward to about the 
same point; in the first uropod the peduncle is much longer than 
the branches, and the outer branch is slightly shorter than the 
inner. The second uropod is similar but has the peduncle much 
shorter, and the difference in length between the two branches 
is slightly greater. The third uropod is greatly elongated ap- 
pearing, however, to differ in length according to the develop- 
ment of the animal. In some specimens examined it is more 
than half the length of the body. The peduncle is long, being 
nearly three times as long as the telson ; the outer branch consists 
of two greatly elongated joints which appear somewhat narrow 
in the side view of the animal but are flattened, the first joint 
being broader than the second and bearing stout setules in slight 
serrations along one margin, the other margin being almost free 
from setae ; the second joint has few setae on its margins but 
a distinct tuft of long hairs at the extremity. The inner branch 
is very small, slightly broadened, and bears a few setules at the 
extremity. 
The telson is cleft to the base, each half oval with a distinct 
spinule at about the middle of the outer margin, another of about 
the same size at the outer portion of the extremity with a mi- 
nute setule nearer the median line. 
The two species Niphargus philippensis and N. chilkensis 
agree in two points in which they differ somewhat markedly 
from the generic diagnosis of Niphargus as given by Stebbing, 
namely : 
