90 
THE VOYAGE OF H.M.S. CHALLENGER. 
It resembles tbe Mithraculus hirsutipes, Kingsley, 1 from Key West, Florida, in the 
four-toothed antero -lateral margins of the carapace, the strongly curved dactyle of the 
ambulatory legs, and in some other characters ; but the ambulatory legs are almost naked, 
not strongly hirsute as in Mithrax hirsutipes, the tubercles of the dorsal surface of the 
carapace are more numerous, and the carpus of the chelipedes tuberculated. 
The carapace is about as long as broad, its dorsal surface nearly smooth and covered 
with scattered tubercles which are disposed as follows ; two immediately behind the base 
of the rostrum, two on the frontal region of the carapace between the orbits, four in a 
transverse series on the gastric region, one in the centre of the cardiac region, two on the 
posterior margin of the carapace (placed one on either side of the median line) and 
several on each branchial region, the largest of which is subspiniform and placed near 
to the postero-lateral margin ; the antero-lateral margins (as already stated) are 
four-toothed ; the first tooth is tuberculiform and placed near to the outer angle of the 
orbit, the three following spiniform, the last the largest. The rostrum is short, rather 
deeply bifid ; there is a strong tooth or spine above the inner angle of the orbit, but 
none at its outer angle, and a rather obscure notch in the middle of its upper and lower 
margins. All the joints of the post-abdomen (in the male) are distinct. The basal 
antennal joint is considerably dilated and has a strong spine at its antero-external angle, 
which spine is visible from above, beneath the spine at the inner angle of the orbit, in a 
dorsal view. The chelipedes are well developed ; the merus and also the carpus armed 
with tubercles above and on the outer surface ; the palm enlarged and laterally 
compressed, but not carinated on its upper and lower margins. The fingers meet only 
at the denticulated apices and have between them a hiatus when closed, and both dactyl 
and pollex are armed besides with three tubercles on their inner margins. The 
ambulatory legs are nearly naked, and are armed (except the dactyli) with strong spines, 
which are strongest on the upper margins of the merus and carpus-joints, and the dactyli 
are strongly incurved near the apices. Colour (in spirit) light reddish-brown above, 
white below ; a longitudinal band of white along the middle of the carapace on the dorsal 
surface. There are a few scattered hairs on the dactyli and penultimate joints of the 
ambulatory legs. 
<?. 
Lines. Millims. 
Length and breadth of carapace, about 
2* 5 
Length of a chelipede, nearly . . 
3 6 
The single specimen (a male) was dredged together with small specimens of 
Mithraculus sculptus at Fernando Noronha, in 7 to 20 fathoms. 
In the strongly tuberculated wrists of the chelipedes and in the spinuliferous 
ambulatory legs, this form resembles Mithrax ursus, Bell, near to which species it must, 
I think, be ranged. 
1 Proc. Acad. Nat. Hci. Philad., p. 147, 1879. 
