PATELLA LIMPET. 1 21 



ginula. In some, the apex is very retuse ; whilst 

 in others it is pointed and elegantly recurved.* 



This genus is peculiarly interesting to those 

 who love to trace the regular, but almost imper- 

 ceptible gradations existing in the scale of nature. 

 The species with the recurved apex seem to form 

 the link which connects the Patellae with spiral 

 shells, whilst the other species, where there is no 

 trace of any volutions, present the intermediate 

 grade between them and the shells entirely desti- 

 tute of spires. 



The animal of the Patella has a large fleshy 

 proboscis, and two tentacula, with the eyes on a 

 small elevation at their base ; the mouth has car- 

 tilaginous plates for the mastication of its food. 

 It has a ventral foot, fleshy, and furnished with 

 numerous muscular filaments, which uniting on 

 the upper part of the mantle, form a strong mus- 

 cle by which the body adheres to the shell. By 

 the action of this muscle, the shell can be brought 

 close to the surface to which the foot adheres, or 

 removed to a distance : and it is by means of this 

 instrument, that the 'animal, when desirous of 

 changing its situation, is able to effect a consi- 

 derable leap. Its locomotive powers however, 

 are but little exercised : it appears to live habit- 

 ually in the same spot, and rarely to perform any 

 other movement than that of slightly elevating 

 its shell, that the water it breathes may reach 



* Plate VI. figure!. 



