124 
THE VOYAGE OF H.M.S. CHALLENGER. 
Xantho, Leach. 
Xantho , Leach, Trans. Linn. Soc. Lond., vol. xi. p. 320, 1815. 
,, Milne Edwards (pt.), Hist. Nat. Crust., vol. i. p. 387, 1834. 
The carapace is transverse and depressed, often nearly flat above, with the dorsal 
surface uneven and lobulated, at least near the front and antero-lateral margins. The 
front projects but slightly beyond the level of the orbits and is usually divided by a 
very small median notch ; the antero-lateral margins are regularly arcuated and are 
divided in the typical species into four or five dentiform lobes, which are not mere 
rounded prominences as in Actsea, and are not produced and spiniform ; in other species 
the marginal teeth are irregular, the orbits are small, and their margins usually bear 
indications of two or three closed fissures. The post-abdomen, in the male, is from five- 
to seven-jointed. The eyes are set on short thick pedicels. The basal antennal joint 
reaches the infero-lateral frontal process, and the flagellum lies within the interior orbital 
hiatus. The exterior maxillipedes present nothing remarkable, having the merus-joint 
distally truncated and usually slightly emarginate at the antero-internal angle. The 
chelipedes (in the typical species) are often considerably developed in the male, usually 
unequal, with the palms but slightly compressed, rounded above, and the fingers dentated 
on the inner margins. The ambulatory legs are of moderate length, and their joints are 
neither carinated nor spinose. 
The species are somewhat numerous and never attain a very large size ; they occur 
commonly on the coasts or islands both of the Atlantic and Indo-Pacific regions, or in 
shallow water. The Challenger collection contains but a single representative of this 
genus. 
The following species are apparently referable to this genus as defined above, and as 
restricted by A. Milne Edwards. It is connected by almost insensible gradations on the 
one hand with Lophoxanthus and Xanthodes, on the other with Panopeus and 
Eurypanopeus. 
/ 
I. Carapace transverse, the front not very prominent ; the antero-lateral margins 
normally toothed, the teeth not rounded (typical species of the genus). 
The genus should perhaps be restricted to include only the species of this section. 
Xantho Jloridus (Mont.) = Cancer poressa, Olivi (?), Cancer incisus, Leach. 
Shores of Europe (70 to 75 metres, A. Milne Edwards). 
Xantho rivalosus, Risso = Cancer hydrophilus, Herbst (?), Europe, northward to 
Slietlands and Scandinavia, 1 5 to 40 fathoms (Heller). 
Xantho tuberculcitus, Bell. Mediterranean and South British Coasts. 
Xantho minor , Dana. Madeira or Cape Verde Islands. 
Xantho pilipes, A. Milne Edwards. Senegal ; Senegambia, Goree Island, 9 to 15 
fathoms. 
