686 L. A. BORRADAILE. 
Subfamily Acanthonychinae. Genus Xenocarcinus White, 1847. 
4, Xenocarcinus tuberculatus White, 1847. Alcock, 1. p. 192. 
Dredged outside Fadifolu Atoll, in 70 fathoms. 
Genus Menaethius H. M.-Edw., 1834. 
5. Menaethius monoceros (Latr.), 1825. Alcock, 1. p. 197. 
A common species, taken in Male, Fadifolu, Minikoi, and Goifurfehendu Atolls down to 
6 fathoms. 
Genus Huenia de Haan, 1837. 
6. Huenia proteus de Haan, 1837. Alcock, 1. p. 195 (Pl. XLVII. figs. 1, 2). 
In the extraordinarily variable shape of its body, this crab is fully worthy of its name. 
The simplest form is found in most of the males, which are flat and triangular, much like 
Menaethius, with a long, sharp rostrum (Pl. XLVII. fig. 1). 
What may be the habitat of these males is yet to be settled: . 
the specimen figured carried a large flat piece of a green weed, SO 
held on its rostrum by means of the hooked hairs always found ee 
there in this species. On the other hand, most of the females 
and some of the males—true males, not “unsexed females” with 
parasites—have the body widened into a leaf-like shape by 
outgrowths of the hepatic and branchial regions (Pl. XLVII. 
fig. 2). These individuals, at least in most cases, live on the 
flat Halimeda-weed, which they closely resemble both in shape 
and colour. Figure 124 is given to show this lkeness. Some of 
the females, however, come near the three-cornered shape of the 
ordinary male. This, and the fact that intermediates are found 
in both sexes, prevents us from callmg the phenomenon 
“dimorphism.” Another interesting feature is shown by the 
walking legs. The last joint in these limbs is strongly toothed, 
and can be shut back at a sharp angle on the one before it. 
In the broad individuals the legs are short and stout and 
keeled to look like the edges of Halimeda “leaves,” and here 

Fie. 124. A sprig of Halimeda-weed 
i 5 = with a specimen of Huenia proteus, 
the whole under-edge of the last joint but one is hairy; but showing the likeness of the latter 
in the triangular form, where the legs are long and slender, toa “leaf” of the weed. 
there is a special tuft of hairs to meet the end-joint, and this 
tuft is often raised on a knob. The whole structure thus formed is all but subchelate and 
seems clearly adapted for holding on by. 
The surface of the body of these crabs may be seen under a high magnification to 
have the curious graving shown in fig. 1a, on Plate XLVI. 
The species was taken in Male Atoll on the reef, and dredged from 22 fathoms in 
Kolumadulu Atoll. 
