368 SUPPLEMENT ON GASTEROPODA. 
in the other gasteropods ; but, in spite of the size of their foot, 
their movements are extremely slow, which is occasioned by 
the thinness of the layer, composed of longitudinal fibres, 
which is the seat of locomotion. But, on the other hand, the 
patellz can adhere to the plane of position in a manner truly 
astonishing. In fact, if previously to removing a patella from 
its rock, it has been first touched, and thus, as it were, ad- 
vertised of the intent, it is impossible to get it away, and the 
shell might sooner be broken, unless a plate of iron be passed 
between the foot of the animal and the rock. It has been 
proved by experiment that a patella will thus support a weight 
of many pounds without falling. This faculty is owing to the 
great quantity of the vertical fibres of the foot, which, by 
raising the middle part form a hollow in the centre, and con- 
sequently a sort of sucker. 
Patella may frequently be observed sunk two or three lines 
in depth in chalky rock, which is singular, considering that 
they do possess, though in a very small degree, the faculty of 
changing place. M. d’Orbigny, however, tells us that each 
individual constantly returns to the same place. From the 
dental apparatus of the patella, and their great abundance 
in places covered with marine plants, it is probable that they 
feed on vegetables. Concerning their reproduction nothing 
is known. ‘They are eaten by some of the poor inhabitants of 
the sea coasts, but their flesh, though savory, is coriaceous 
and indigestible. 
With respect to the OSCABRIONS (CHITON) though their 
organization is very remarkable, we know little or nothing of 
their manners. 
