300 
THE VOYAGE OF H.M.S. CHALLENGER. 
Arcania septemspinosa (Fabricius). 
Cancer septemspinosus, Fabricius, Mantissa Insectorum, vol. i. p. 325, 1787. 
Iphis septemspinosa, Leach, Zool. Miscell., vol. iii. p. 25, 1817. 
„ „ Milne Edwards, Hist. Nat. Crust., vol. ii. p. 139, 1837 ; Atlas in Regne 
Animal de Cuvier, ed. 3, Crust., pi. xxv. fig. 4 (after Herbst). 
„ ,, Bell, Trans. Linn. Soc. Lond., vol. xxi. p. 311, 1855; Cat. Leucosiidae in 
Brit. Mus., p. 22, 1855. 
Hong Kong, 10 fathoms (an adult and two younger females) ; Kobe, Japan, 8 to 10 
fathoms (a small female); and at Station 233b, in lat. 34° 18' 0" N., long. 133° 35' 0" E., 
15 fathoms (a young female and two rather small males). 
The largest male measures as follows : — 
d . Lines. Millims. 
Length of carapace, nearly . . . . . . 7 14 - 5 
Breadth of carapace, nearly . . . . . . 6J 1 3 - 5 
The genus Iphis, wdiich is retained as distinct from Arcania, both by Milne Edwards 
and Bell, differs merely in its slightly more rhomboidal carapace, and must, I think, be 
united with that genus. 
Ixa, Leach. 
Ixa, Leach, Trans. Linn. Soc. Lond., vol. xi. p. 334, 1815. 
„ Milne Edwards, Hist. Nat. Crust., vol. ii. p. 134, 1837. 
,, Dana, U.S. Explor. Exped., vol. xiii., Crust. 1, p. 392, 1852. 
„ Bell, Trans. Linn. Soc. Lond. (Zool.), vol. xxi. p. 311, 1855. 
Carapace transversely rhomboidal, or somewhat elliptical, and prolonged at the 
junction of the antero-lateral and postero-lateral margins into a cylindrical lobe, which 
often equals in length the transverse width of the carapace, and is rounded or tipped 
with a spinule at the distal extremity ; the carapace is usually longitudinally divided 
into three parts by two wide fossae, which border the cardiac, gastric, and hepatic regions, 
and thence are continued over the pterygostomian regions to the bases of the chelipedes, 
but these fossae are sometimes obsolete. The front projects but slightly, and is anteriorly 
concave ; the orbits have three marginal fissures and a rather wide interior hiatus. The 
endostomian ridges are strongly defined, and the channels exterior to them, communi- 
cating with the branchial cavities, are emarginate at the distal extremity. The post- 
abdomen (in the male) covers the sternum at base, and is five-jointed, with three of the 
intermediate segments coalescent. Eyes small. Antennules slightly oblique. Antennae 
with the basal joint very slender and not filling the interior hiatus of the orbit. The 
endognath of the exterior maxillipedes is narrow, with the ischium longitudinally 
sul cated, the merus triangulate ; the exognath is broad, with the exterior margin straight ; 
it is rounded at the distal extremity, and does not wholly cover the channel which 
communicates with the branchiae. The chelipedes (in the male) are cylindrical and very 
