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Scientific Memoirs by

      Among Oxystome crabs that have this singularly effectual disguise are
Oreophorus reticulatus and alcicornis, Actœomorpha morum and lapillulus,
Tlos petræus and patella, and Heterolithadia fallax.

      Among Oxyrhynch crabs, Parthenope horrida and investigatoris, all the
species of the sub-genus Parthenolambrus and several of the species of the
subgenera Rhinolambrus and Platylambrus.

      Even among the Cyclometopes, which, as a group are fierce and active
crabs, there are some that have this protective resemblance to the inanimate
objects among which they shelter themselves: such are several of the species of
Carpilodes (notably C. cariosus), of Lophactœa, of Leptocius and of Actœa (not-
ably A. flosculata, A. echinus, A. nodulosa, A. fossulata).

      Among Catometopes, I only know of one genus that leads a retiring life
among coral-shingle at the bottom of the sea, and that is the aberrant Palicu
(Cymopolia): two, at least, of the Indian species of this genus might easily be
mistaken for flakes of eroded coral-rock.

      Others of these small shingle-haunting crabs have a striking resemblance to
another common constituent of the shingle of tropical seas, namely, broken shells,
discoloured and encrusted. I have noticed this form of protective disguise in
several species of the Oxystome genera Nursia and Nursilia, and in the
Oxyrhynchs Cryptopodia, Heterocrypta and Micippa.

      In all the foregoing cases the disguise may be supposed to be the passive
results of sculpture and colouration coming out on a torpid organism. In other
cases—too well known and too numerous to refer to—weak and inoffensive crabs
of a sluggish habit take steps, as if by design, to conceal themselves, The
Oxyrhynch crab Camposcia retusa, which covers itself with a patchwork coat
of scraps of sea-weed, is one of the best known illustrations of this apparently
deliberate method.

      Every naturalist must have observed instances for himself: I may mention
the two best cases that have come to my notice, namely, the two Oxyrhynchs
Chlorinoides longispinis and Macrocœlonma nummifer. Both these species make
great use of the shells of Orbitolites in constructing their protective mantle-
But in Chlorinoides longispinis the carapace is also armed with long slender
spines, each of which ends in an elegant knob, and when the crab is covered with
Orbitolite shells and pieces of sea-weed, these curious spines stick out, as from an
encrusted rock, like a group of Hydroid polyps with their tentacles retracted.

      The singular form of the carapace of the female of the Oxyrhynch crab
Huenia proteus, is undoubtedly a protective disguise of a similar kind. The
carapace is flat and depressed, and its angles are produced to form rather rag-
ged crinkled lobes, which both in form and colour resemble fronds of fucus.