PATELLA LIMPET. 119 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shells of this genus are easily distin- 

 guished from all others by their conical form and 

 dilated aperture ; but they are subject to many 

 peculiarities, and are therefore divided into se- 

 veral natural groups. Some are remarkable for 

 an internal chamber or partition, which however 

 varies greatly in its appearance. In the Patellae, 

 called the Slippers, it is formed by the columel- 

 lar lip, which is straight and produced into a flat 

 horizontal plate extending half over the mouth 

 of the shell. In others, this appendage resem- 

 bles a cup situated at the apex within the shell, 

 and the Limpet bearing it is called from its shape 

 the Cup and Saucer Limpet.* The apex of 

 many of the Patellae is perforated,! and this 

 peculiarity in the shell is connected with a diffe- 

 rent formation of the animal, whose gills are 

 situated near the holes through which it receives 

 the needful supply of water. In some, the apex 

 is very retuse ; whilst in others it is pointed and 

 elegantly recurved. J 



This genus is peculiarly interesting to those 

 who love to trace the regular, but almost imper- 

 ceptible gradations existing in the scale of na- 

 ture. The species with the recurved apex seem 

 to form the link which connects the Patella? with 

 spiral shells, whilst the other species, where 



* Plate V. figure 7. t Plate V. figure 8. 



| Plate VI. figure 1. 



