120 UNIVALVES. 



Genus PATELLA.* Plural, Patella. 



LIMPET. 



Generic Character. Shell univalve, without a 

 regular spire, dilated, conical, entire, concave 

 beneath in proportion as it is convex above. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shells of this genus are easily distinguished 

 from all others by their conical form and dilated 

 aperture ; but they are subject to many pecu- 

 liarities, and are therefore divided into several 

 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 ; these now form a genus 

 called Crepidula. In others, this appendage re- 

 sembles a cup and is situated at the apex within 

 the shell, which is commonly called from its shape 

 the Cup and Saucer Limpet ; f it is now sepa- 

 rated from the Patellae and forms the genus 

 Calyptraea. The apex of many of the Patellae 

 is perforated,! and this peculiarity in the shell 



* Plate V. figure 7, 8, and Plate VI. figure 1. 

 f Plate V. figure 7. J Plate V. figure 8. 



