and is armed with five ftrong teeth, of a fharpened 
form : the ftomach and inteftines, which are of con- 
fiderable length, are difpofed in a fomewhat circu¬ 
lar diredlion, and the Avhole body is fupported in¬ 
ternally by a fet of upright bones or columns. On 
the outfide of the fhell are feated a prodigious num¬ 
ber of fharp, moveable fpines, curioufly articulated 
with the tubercles on the furface, and connecled by 
ftrong ligaments to the fkin or epidermis with which 
the fhell is covered. Thefe are the inftruments of 
motion, by the afliflance of which the animal con¬ 
veys itfelf at pleafure to any particular fpot; and 
fo tenacious are they of the vital principle, that on 
opening the animal, it is no very uncommon cir- 
cumftance to obferve the feveral parts of the broken 
fhell walk off in different direcftions. Between the 
fpines, difpofed in a continued longitudinal feries 
on the feveral divifions or regions of the fliell, are 
an infinite number of very fmall foramina, com¬ 
municating with an equal number of tentacula, 
placed above them. Thefe are the inftruments by 
which the creature affixes itfelf to any objecfl, and 
flops its motion. They are polfeffed of a very high 
degree of contracilile power, and are furnifhed at 
the extremities with an expanfile part, which may 
be fuppofed to operate as a fphincler, or as the 
tail of a leech, and to faflen the animal fecurely to 
rocks, or other fubflances to which it choofes to 
adhere. 
The general color of the common echinus, when 
covered with its fpines, is a dull violet; though 
fome- 
