216 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



9. Rostrum distinctly bifid at its tip; genital segment with only 



faint lateral indications of division intermedius (p. 226) 



Rostrum not bifid at tip ; genital segment distinctly divided 



through its center commensalis (p. 227) 



MALES 



1. Terminal segment of fifth legs with 6 marginal setae, third 



inner one nonplumose and hairlike 2 



Terminal segment of fifth legs with 5 marginal setae, middle 



one nonplumose and hairlike 5 



Terminal segment of fifth legs with 4 marginal setae, 2 inner 



plumose, third filiform, fourth spiniform dacty lifer, new species (p. 223) 



2. Second basipod of first legs with 1 long spine at inner corner, 



reaching beyond center of basal endopod segment 3 



Second basipod of first legs with 2 or more short spines on inner 

 margin, not reaching base of basal endopod segment 4 



3. Long spine bent abruptly outward beyond its center ; second, 



third, and fourth metasome segments pink, rest of body 



white cinctus (p. 221) 



Long spine curved inward ; entire body behind cephalic segment 



a dark chocolate-brown obscurus (p. 216) 



4. Inner margin of second basipod of first legs with 4 equal short, 



straight, and sharply pointed spines longirostris (p. 217) 



Inner margin of second basipod of first legs with small proximal 



knob and 2 blunt spines, sometimes fused pallidas (p. 219) 



Inner margin of second basipod of first legs with small proximal 



knob and 1 curved blunt spine attenuatus (p. 218) 



5. Basal expansion of fifth legs short and broad, not reaching center 



of distal segment; 2 or 3 short unequal setae hispidus (p. 225) 



Basal expansion of fifth legs long and narrow, reaching tip of 



distal segment; 2 long and equal setae sinuatus (]). 222) 



Basal expansion of fifth legs short and broad, reaching beyond 



center of distal segment; 2 medium equal setae commensalis (p. 227) 



AMPHIASCUS OBSCURUS Sars 



Figure 144 

 Amphdascus obscurus Saes, Crustacea of Norway, vol. 5, p. 150, pi. 93, 1906. 



Occurrence. — A few specimens of both sexes were found in two of 

 the brackish ponds on Chappaquiddick Island. 



Distribution. — ^Norwegian coast (Sars) ; Woods Hole Harbor 

 (Fish). 



Color. — Dorsal surface of cephalic segment light yellow tinged 

 with brown; the rest of the body a dark chocolate-brown, changing 

 into deep indigo-blue on the caudal rami and the ventral appendages; 

 eye bright red. 



Female. — Cephalic segment as long as the rest of the metasome; 

 rostrum elongate triangular, bluntly pointed; segments of urosome 

 fringed with coarse spinules along their posterior margins on tho 

 ventral and lateral surfaces; caudal rami wider than long, massive 

 and close together. First exopod three-fourths as long as basal 

 endopod segment; end segment of third exopod with four setae and 



