ISOPODA. 15 
The crustaceous character of the mesosome is an exceedingly variable feature. 
Usually the first four segments show it very clearly ; in the two following it is usually 
concealed. The fourth segment frequently has a conspicuous and quadrangular space 
in the mid-dorsal line, but as frequently this is quite absent. The succeeding segment 
also bears evidence of a median division, but often it is only partly crustaceous. The 
sixth segment is rarely crustaceous, but when it is the deposit is not evenly deposited. 
This segment only rarely exhibits the rounded postero-lateral margins so characteristic 
of the ‘Southern Cross’ species; but here, on turning the animal on to the dorsal 
surface, traces of the button-like process may be detected. 
Numerous specimens, male and female and all ages, were taken from the roots of 
sponges inside the 25-fathom line. A few were taken at a time during the whole of 
our stay in Winter Quarters. 
EUNEOGNATHIA. 
This genus was separated from the more widely-known genus Gnathia by the 
Rev. T. R. R. Stebbing, on the ground that the first gnathopod of the male is 
six-jointed, and that the pleopods have both branches fringed with long plumose hairs. 
EUNEOGNATHIA GIGAS. 
Anceus gigas Beddard (1), pp. 137-9. 
Euneognathia gigas Stebbing (15), p. 338. 
Specific characters :— 
Hale. 
Cephalosome short and broad, with a sinuous anterior margin and a short spur laterally. 
Depressed in the centre and tuberculated externally. 
Maxilliped with 4-jointed palp, setose externally. 
Gnathopods 6-jointed, with long sete: externally, short ones internally. 
The single specimen measures some 16 mm. in length, the same size as the 
Anceus gigas described by Mr. Beddard in the Isopoda of the ‘Challenger’ Reports. 
The following description will show that it must be identified with that species. 
The cephalosome is broad, rounded postero-laterally, and has a prominent spur 
at the antero-lateral angle external to the antennz and just in front of the eyes. 
The anterior margin is sinuous, due to fine, small tubercular enlargements. The 
middle one is the smallest, and is slightly indented. Its surface is rather depressed 
anteriorly, but abreast and behind the eyes are two prominent tubercles on each side, 
of which the posterior is much the larger, and this latter is separated by a smooth 
narrow portion from the tumid posterior margin of the cephalosome. Mr. Beddard’s 
specimen is not satisfactorily figured. The anterior margin of the cephalosome is 
similar to that of the ‘ Discovery’ specimen, but the tubercles are more exaggerated. 
The ovoid lobes connected with the eyes do not exist as figured, but in place of them 
are two prominent swellings, the surface of which is coarsely tuberculated. 
