PARASITIC HABITS OF CRUSTACEA. 247 
from Ceylon, which are probably made by another species of 
the same genus. The genera Trapezia and Tetralia include 
small, smooth and polished, usually bright-colored crabs, 
which live free among the branches of Pocillipora and Ma- 
drepora. For this mode of life they are well adapted, both 
by their smooth, flat bodies, and by their peculiar feet, which 
are blunt at the end and furnished with sharp stiff spines to 
aid them in climbing among the coral branches. Domecia 
hispida has the same habits. 
The Hermit or Soldier Crabs, are interesting in their 
habits, and well known to all sea-side naturalists. They 
always occupy the dead shell of some spiral Gasteropod, 
which they carry about on their backs, and into which they 
retreat when alarmed, holding it firmly by means of the 
long, spirally-curved abdomen, and by its hook-like appen- 
ages. But some species are apparently not satisfied with 
even this protection, and consequently induce certain species 
of Sea-anemones to dwell upon the shell they inhabit. The 
beautiful Sea-anemones belonging to the genera, Adamsia 
and Calliactis, are rarely found except in this situation. 
Adamsia maculata, of the European coast, attaches itself to 
the shell occupied by Zupagurus Prideauzii, near the inner 
lip, and spreads out its base laterally on each side until the 
lobes thus formed meet around the aperture and coalesce so 
as to form a complete ring, through which the crab emerges 
and retreats. The base of this Adamsia also has the unusual 
Power of secreting a thin but firm pellicle, by which it ex- 
tends the edges of the aperture of the shell, thus giving the 
crab more room, as it grows larger, and obviating the ne- 
cessity of changing the shell, as other less-favored hermits 
Are obliged to do. Several specimens of Calliactis usually 
occupy the same shell, and are not known to be capable of 
extending its aperture. All the species are very beautifully 
Colored, and inhabit tropical seas. In the West Indies C. 
; bicolor and C. tricolor are common, and one species occurs at 
Florida, while C. variegata occurs at Panama. i$ sol 






























