682 L. A. BORRADAILE. 
typical members of the Oxyrhyncha—the Maiidae'—have adopted another plan. They hide 
themselves by covering their bodies with bits of seaweeds, zoophytes, or sponges, which are 
held on by hooked or jagged hairs of special shape found on the body and limbs of the 
true spider-crabs and not elsewhere (Pl. XLVII. figs. 3c and 4d). They are gathered and 
placed in position by the crab itself, which uses for this purpose its chelipeds. These limbs 
are specially shaped so as to have a mobility not found in other crabs, and are thus able 
to reach distant parts of the body and legs. In order that they may adhere better, the 
fragments of weed, etc. are treated with a secretion given out by glands on the first 
maxilliped?; and they not only remain in a living state, but often continue to grow, so 
that in some genera it is not uncommon to find the whole crab as completely hidden by 
a single sponge as any Dromia. Besides seaweeds, the organisms used include sponges, 
hydroids, polyzoa, and ascidians, and in some cases barnacles and tubicolous worms add 
themselves as self-invited guests. Several different kinds of organisms may sometimes be 
found on the back of one crab, but in most cases, very possibly in all, the species planted 
by it are those amongst which it is living and are changed if it be placed in other 
surroundings where they would be conspicuous. This implies considerable care in the choice 
of the clothing, and indeed such may easily be seen to be bestowed if a captive individual, 
say a Maia squinado, be watched while it is disguising itself. I have even seen this species 
cover its back with shingle when no weed was available. The number of hairs naturally 
varies, as does also the extent to which the crab is hidden, but it rarely happens (pzaltus) 
that they are quite wanting. 
1 Key to the families of the Oxyrhyncha. Second joint of antenna truncate-triangular. Hye- 
I. Carapace thin and flat. First leg (cheliped) not long or stalks very short. Acanthonychinae. 
specially mobile or with fingers bent at an angle with the B. True orbits, containing both supra- and postocular 
hand. Male opening sternal. [No orbits. Second joint elements sheltering the eyes, are more or less com- 
of antennal stalk slender, fused with epistome but not pletely formed, except in a few genera where the 
with front. No hooked hairs. ] Hymenosomidae. eyestalks are long and slender. Second antenna-joint 
II. Carapace not thin and flat (except Ocinopus). First leg broad, usually not truncate-triangular. Hyestalks long 
either mobile or powerful with bent fingers. Male opening or short. 
coxal. 1. A large, cupped, usually blunt postocular process 
A. Chelipeds specially mobile, rarely much larger than present. Eyestalks short. Cornea of eyes not com- 
the other legs or with fingers bent at an angle on the pletely hidden when they are folded back. Pisinae. 
hand. Second joint of antenna well developed, generally 2. Postocular process, if present, usually sharp and not 
fused with epistome and often with front. Orbits eupped, but if not so then cornea hidden (as also 
generally more or less incomplete. Hooked hairs in most other cases). Eyestalks usually long. 
almost always present. Maiidae. Matinae. 
B. Chelipeds not specially mobile, usually much longer 
and heavier than the other legs and with fingers bent Key to the subfamilies of the Parthenopidae. 
on the hand at an angle towards the side on which I. Carapace usually triangular, sometimes suboval or sub- 
the fixed finger is set. Second joint of antenna small, pentagonal. Rostrum simple. Chelipeds much bigger 
short, and not fused with epistome or front. Orbits than the other legs. Branchial regions of the body 
well made. Hooked hairs almost always wanting. deeply separated from cardiac, Parthenopinae. 
Parthenopidae. II. Carapace usually sharply pentagonal. Rostrum cleft 
Key to the subfamilies of the Maiidae. into ne june pad ee Ree 
I. Second joint of antenna very slender throughout its length. cet i aa tas erase ohh ganze att oo 
[No crete Eyestalks generally long.] COE: 2 For an account of those structures in the Spider-Crabs 
II. Second joint of antenna not very slender. which are specially adapted to their habit of clothing them- 
A. No true orbits (eyestalks hidden under a supraocular selves, see Aurivillius, Kong. Svenska Vet.-Ak. Hand. Bt. 
spine or sunken in the sides of a great rostrum). xxu1. no. 4 (1889), 
