184 
THE VOYAGE OF H.M.S. CHALLENGER. 
Milne Edwards as characteristic of his Xiphonectes leptocheles than in the smaller 
specimen with slender chelipedes . 1 
The dimensions of the specimens are as follows: — 
6. 
Lines. 
Millims. 
Length of carapace, about 
4 
9 
Breadth of carapace, nearly 
H 
9-5 
Length of lateral spine, nearly 
3 
6 
Length of a chelipede, about . 
9 
19 
Young <£. 
Length of carapace, nearly 
3 
6 
Breadth of carapace, nearly 
H 
7-5 
Length of lateral spine, about . 
H 
5 
Length of a chelipede, about . 
8 
17-5 
Scylla, de Haan. 
Scijlla, de Haan, Crust, in v. Siebold, Fauna Japonica, decas i. p. 11, 1833. 
,, A. Milne Edwards, Archiv. Mus. Hist. Nat., vol. x. p. 347, 1861. 
This genus is very nearly allied to Neptunus, but is distinguished by its smoother, 
more convex carapace, which is not marked by the transverse raised lines which are 
characteristic of that genus, except by one on each side which are prolonged inwards for a 
short distance from the base of the lateral epibranchial tooth. The front is armed with 
six lobes or teeth, which are much more prominent in the young than in the adult animal. 
The antero-lateral margins are oblique, as in the typical Neptuni, and are armed with 
nine lobes or teeth, but the last (lateral epibranchial) tooth is not at all longer than 
those which precede it. The epistoma is distinctly developed. The post-abdomen in the 
male is subtriangulate, with the lateral margins nearly straight and convergent from the 
anterior margin of the third segment, which, with the fourth and fifth, is consolidated 
into a single joint. The eye-peduncles are of moderate thickness. The basal antennal 
joint is somewhat dilated, and barely reaches the front, it is prolonged at its antero- 
external angle into a lobe, which does not, as in Gonisoma, exclude the flagellum from 
the orbital hiatus. The merus of the exterior maxillipedes is obliquely truncated at the 
antero-internal angle, slightly rounded at the distal extremity, with the antero-external 
angle but little prominent and subacute. The chelipedes in the adult male are large 
and massive, and sometimes unequally developed ; merus, carpus, and palm, are armed 
with spines, but the exterior surface of the carpus and palm are not longitudinally 
cristated as in Neptunus, and the palm is shorter and more turgid, the fingers strongly 
toothed on the inner margins, and the dactylus distinctly arcuated. The ambulatory 
1 In the Report on the Crustacea of H.M.S. “ Alert,” before seeing the Challenger specimens, I regarded the three 
described species of Xiphonectes as distinct. 
