126 
THE YOYAGE OF H.M.S. CHALLENGER. 
Xantho bidentatus, A. Milne Edwards (PI. XI. fig. 4). 
1 Xantho bidentatus, A. Milne Edwards, Ann. Soc. Entom. France, ser. 4, vol. vii. p. 266, 
1867. 
The body and limbs are nearly naked, only the pterygostomian regions and the three 
last joints of the ambulatory legs being partly clothed with a very short close pubescence ; 
the j oints of the ambulatory legs also are fringed with a few longer hairs. The carapace 
is transverse, slightly convex, smooth and shining, and is very faintly lobulated on the 
postfrontal, the hepatic, and the front of the gastric and branchial regions ; the cardiac 
and the posterior part of the branchial regions are nearly smooth, the cervical and other 
sutures of the anterior part of the carapace are distinct but not deep. The frontal margin 
is divided by a small median notch into two truncated and slightly sinuated lobes, which 
project slightly over the antennulary septa and beyond the inner angles of the orbits, 
which are not at all prominent ; the orbital margins are entire, the antero-lateral margins 
of the carapace are rather shorter than the postero-lateral margins, and are armed only 
with two distinct teeth, the fourth and fifth of the normal series ; in front of these, two 
very obscure prominences indicate the position of the second and third antero-lateral 
teeth. The post-abdomen, in the male, is five-jointed, the third to the fifth joints coalescent. 
The eyes are small; the basal joint of the antennae is but little longer than broad, and its 
antero-internal angle is in contact, as is usual in the genus, with the infero-lateral process 
of the frontal margin ; the ischium -joint of the outer maxillipedes is marked on its outer 
surface with a longitudinal, impressed, and slightly sinuated line ; the merus-joint is some- 
what transverse, slightly emarginate at its antero-internal angle; the exognath does not 
reach to the distal extremity of the merus-joint. The chelipedes, in the male, are smooth 
and polished ; the merus or arm very short, trigonous ; carpus with an angulated prominence 
on its inner surface, palm smooth, both on its outer and inner surfaces, with the upper 
margin rounded, its outer surface rather convex, with scattered punctulations ; fingers 
denticulated on their inner margins and with acute apices ; the ambulatory legs are 
relatively rather slender and compressed. Colour (in spirit) yellowish-brown ; the 
fingers dark-brown or nearly black ; the colour of the lower finger extends for a very 
short distance inwards over the inner and outer surfaces of the palm. 
Adult $ . 
Lines. 
Millims. 
Length of carapace, rather over 
4 
9 
Greatest breadth, ..... 
6 
12-5 
Length of larger chelipede, about 
8 
17 
Length of second ambulatory leg, nearly 
61 
14 
The unique specimen (a male) was obtained on the beach at Samboangan, in the 
Philippines. 
This species is characterised by the smooth and shining surface of the carapace, 
which, viewed with the microscope, is seen to be closely and minutely punctulated, by 
