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THE AUSTRALIAN MUSEUM MAGAZINE. 



effected by means of the nippers, which 

 curiously are never covered. Some- 

 times, however, mere pruning is in- 

 effectual in controlling the growth of an 

 ill-chosen cloak, and then the unfor- 

 tunate bearer has to await the seasonal 

 moulting, when the encumbrance is 

 shed along with the disca ded shell. 



Harlequin Crabs (Camposcia retusa). The 

 upper example is disguised with a cloak of 

 seaweed and sponges. Below is depicted a 

 half denuded specimen, showing the stiff 

 hooked hairs on one side and a dense mass 

 of conglomerate sponge growth on the other. 

 [Photo. — O. C. Cliitton. 



A near relative of the foregoing is 

 the Harlequin Crab (Camposcia re- 

 tusa) of the tropical Australian coast, 

 which also possesses a growth of hooked 

 hairs ; but these are much denser and 

 coarser than those of the Sponge Crab. 

 This species gathers unto itself a 

 marvellously varied assortment of 

 marine growths which cover it with a 

 coat of many colours. The covering 

 completely harmonises with the brightly 

 tinted objects amongst which the 

 Harlequin lives, and provides means of 

 escaping unnoticed in any sudden 

 emergency or disarms suspicion in the 

 case of smaller prey. The Harlequin 

 Crab stands alone amongst its kind as a 

 master of disguise, and, as it lies quietly 

 at the bottom of a shallow coral pool, 

 with its legs and nippers (chelae) tucked 

 in close to the rest of the body, its real 



identity is often unrecognised by the 

 human eye. Collectors have time and 

 again grasped what they supposed to be 

 a beautiful conglomerate mass of marine 

 life, only to discover that what they 

 held was mostly crab. 



With regard to the protective re- 

 semblance of form, it will be as well to 

 mention here the peculiar adajitation 

 of another Spider Crab called Huenia 

 jyroteus, a species which exhibits a most 

 striking example of modification in ex- 

 ternal structure. The carapace or shell 

 is flat and extraordinarily variable 

 in shape. In most of the males it is 

 more or less triangular in outline, but 

 in the majority of the females as well 

 as in some males, it is broadened by 

 leaf-like expansions of the lateral 

 edges. This crab commonly lives among 

 the seeweed, Halimeda, to the fronds 

 of which it bears a striking resemblance 

 in both form and colour. It is found 

 only i 1 the shallow reef waters of the 

 Indian and Pacific Oceans. 



The Halimeda Spider Crab (Huenia proteus), 

 photographed alongside a portion of the 

 seaweed from which it derives its name. 



[Photo. — G. C. Glutton. 



Among other crabs possessing the 

 same habit of hiding underneath por- 

 table coverings are several species 

 included in two allied families known 

 as the Dromiidae and Dorippidae. 

 In the former the various members 

 lead a more or less sedentary life. 

 The adults have the last pair or the 

 last two pairs of legs short and placed in 

 a most unusual position over the back, 

 where they serve to hold a mass of 

 living sponge or other marine growth. 



