220 



THE SEA SHORE 



natives of tropical seas, but several are common on our own 

 shores. 



One species of the typical genus is sometimes found off the 

 coasts of Cornwall and Devon. The shell is very oblique, and the 

 valves are unequal, the right one, on which the animal rests, being 

 somewhat smaller than the left ; and the epidermis is very scanty. 



Fro. 152. Avicula, AND Pinna pectinata 



The hinge is long and straight, without teeth, and the cartilage is 

 contained in grooves. The interior of the shell is pearly. The 

 posterior adductor impression is large, and not far from the middle 

 of the shell, while the anterior, which is small, is close to the um- 

 bones. The mantle of the animal is open, and the margins of the 

 lobes fringed ; and the small foot spins a powerful byssus. 



Most of the British species of the family belong to the genus 



