ANCEUS HALIDAII. 203 
ISOPODA. ANCEID.2. 
ABERRANTIA, 

ANCEUS HALIDAII. 
Specific character. Male, with the cephalon nearly square, the lateral 
anterior angles truncated for the insertion of the antennx, middle of the fore 
margin produced into three broad divisions, of which the central is slightly 
porrected ; margin finely serrated ; antero-dorsal surface of cephalon very 
broadly concave ; mandibles small, scarcely half the length of the cephalon, 
entire on the outer margin; second pair of gnathopoda composed of five broad 
joints. Male exserted organ rather short and thick; pereiopoda with small 
spines on the terminal joints. 
Female, with the outer gnathopoda five-jointed, narrower than in the 
male; inner gnathopoda wanting? 
Length, one quarter of an inch. 
Anceus formica? Hxssz, Mém. trang. Acad. Sci. t. xviii. p. 89, pl. iii. 
figs. 5, 6, 7. 
THIs species is at once distinguished from A. mazil- 
laris by the very different structure and small size of 
the mandibles and foot-jaws in the males, and by the 
latter character as well as the (apparent) want of the 
inner pair of foot-jaws in the females. The head of 
