338 THE INHABITANTS OF THE SEA. 
It is large enough to admit of the creature’s rising a little, but 
not of its coming out easily. The echinus adheres so firmly to 
this cavity by its suckers, as to be forced from it with extreme 
difficulty when alive. On the coasts of the county of Clare 
thousands may be seen lodged in the rock, their purple spines 
and regular forms presenting a most beautiful appearance on 
the bottoms of the grey limestone rock-pools. How the boring 
is performed has, like many other secrets, not yet been settled by 
naturalists. The first perforation is most likely effected by 
means of the teeth, and then the rock softened by some secreted 
solvent. 
Sea-urchins are found in all seas, but as they are extremely 
difficult to preserve, and many of them have such long and deli- 
cate spines that it is almost impossible 
to procure perfect specimens, probably 
not one tithe of their species is known. 
On our coasts the common “ egg-ur- 
chin” affords the poor a somewhat scanty 
repast ; but, throughout the Mediterra- 
nean, its greater size, and also that of its 
allies, Echinus melo and KE. sardicus, 
Mammillated Sea-Urchin. Hae oh) 
render them, when “in egg,” important 
articles of food. In Sicily these animals are in season about the 
full moon of March; there the £. esculentus is still called the 
« King of Urchins ;” whilst the larger melon-urchin is popularly 
considered to be its mother. The size and abundance of these 
edible species are among the striking peculiarities of the fish 
markets of the Mediterranean sea-board. 
The calcareous shell of the “sea-urchin” seems, at first sight, 
to be composed of one simple crust, but proves, on nearer in- 
spection, to be a masterpiece of mosaic 
consisting of several hundred parts, 
mostly pentagonal. These are so closely 
united that their junctions are hardly 
visible, but on allowing the shell to 
macerate for some days in fresh water, 
it falls to pieces. This complicated 
structure is by no means a mere archi- 
tectural fancy, a useless exuberance of ornament, but essen- 
tially necessary to the requirements of the animal’s growth. A 
simple hard crust would not have been capable of distension, 
Edible Sea-Urchin. 
