cies into which it is divided; the number of which 
is fo great that it is found entirely neceftary to fub- 
divide them into fedlions according to their diffe¬ 
rent fhape or general habit, in order that they may 
the more readily be inveftigated. Some are of a 
fhort, thick, and nearly orbicular form, and fomc- 
times the tranfverfe diameter of their body confide- 
rably exceeds the longitudinal: others are of a thin 
and long form: fomc are ftrongly muricated; others 
perfectly fmooth : fome are furnifhed with very 
firong and large chelae or claws; others have only 
weak, unarmed feet: laftly, fome are remarkable 
for their great fize, while others are fo diminutive 
as to require the affiftance of glalfes in order to 
determine the ftrudture of their feveral parts. 
The animals of this genus caft their fliells from 
time to time. When this period approaches, the 
limbs gradually fhrink or wafte in fize, fo as to en¬ 
able them to be drawn with the greater eafe from 
the claws and other parts of the (hell. The animal 
then lies in a quiet ftate for fome days, till the new 
fhell is formed, or rather till it is hardened; for at 
firft it is rather membranaceous than cruftaceous. 
I he lofs of a limb, an accident fo dreadful and ir¬ 
remediable to the major part of the animal world, 
is to thefe creatures of but little importance; fince 
the fpace ot a few weeks fupplies the defedt, and 
reftores them to their former ftate. What is ftill 
more wonderful, thefe animals, when injured, maim¬ 
ed, or bruifed on any particular limb, do not w r ait 
foi the procefs of a gradual recovery of that indivi¬ 
dual part, but, as if confcious of the power of re¬ 
production. 
