520 27z.e Philippine Journal of Science 1920 
1. The inner lobe of the first maxilla is large and broad and 
bears many plumose setae. 
2. The second gnathopod is larger than the first, and differs 
considerably from it in shape. 
In his generic diagnosis Stebbing(4) (p. 405) says: “Maxilla 
1, inner plate with few (2 or 3) setae” and “Gnathopods 1 and 2 
similar.” In N. pulchellus [Sayce(3) (p. 152)] from Australia 
the inner plate of the first maxilla is broad and with numerous 
setae, but in that species the first and second gnathopods are 
similar and subequal. The gnathopods in N. chilkensis and 
N. philippensis present a rather striking resemblance to those 
of Phreatogammarus propinquus Chilton from New Zealand (2) 
(p. 84), and also resemble those of Metacrangonyx longipes 
Chevreux(l) (p. 27), found in the Balearic Isles, more than they 
do those of typical species of Niphargus. In Phreatogammarus 
and in Metaa-angonyx the third uropods are, however, very 
different from those of Niphargus, being elongated with equal 
branches in Phreatogammarus, and very short with inner branch 
vestigial in Metacrangonyx. The third uropods are, however, 
subject to much modification in all subterranean species, and 
possibly the gnathopods are more trustworthy as evidence of 
relationship than the variable terminal uropods. 
Niphargus philippensis, although resembling N. chilkensis in 
the first maxilla, the shape of the gnathopods and particularly 
in the setose character of the ischium of the first gnathopod, 
differs in the following points, most of which have already been 
mentioned, namely: 
1. In the absence of eyes. 
2. In the different shape and size of the branchiae. 
3. In the shape of the first antenna, especially in the second 
joint of the peduncle and the long thickened flagellum. 
4. In antenna 2, the joints of the flagellum being distinct and 
not fused as in N. chilkensis. 
5. In the broadened basal joints of peraeopods 1 and 2. 
6. In the basal joint of the fifth peraeopod, which is normal and 
not greatly enlarged, while in N. chilkensis the basal joint may 
be very large and longer than all the succeeding ones. In N. 
chilkensis, too, the joints of the three posterior pairs of peraeopods 
show a greater tendency to be broadened, the merus especially so. 
7. In the third uropods, which are more elongated in N. phil- 
ippensis and not quite so broad in proportion as N. chilkensis. 
An examination of the different specimens of Niphargus phil- 
ippensis shows that there is considerable variation in the length 
