522 DESCRIPTION OF THE MUSEUM. 



4th. The family of the pectinidece comprehend- 

 ing seven genera. The first , peditm, is composed 

 of only one very valuable species from the Indian 

 seas. We have forty-six species of the genus 

 pecten, all fine and brilliant shells. The most rare 

 and beautiful amongst them are the ducal mantle, 

 the sole, and the bishop's mantle (p. bifrons, 

 Lam). The spondyli \\a\z still more brilliant co- 

 lours; there are nineteen species in the collec- 

 tion, amongst which we shall notice the radians 

 and the longispina. 



5th. The family of the ostracece, composed of 

 the genera gryphcea, ostrea, vulsella, placuna 

 and anomia. We have sixty species of the second 

 genus and five or six of each of the others. It 

 was long supposed that these shells existed only 

 in a fossil state ; but we now have one, the giy- 

 phcea angulata which is recent and is considered 

 as very rare and valuable. The vulsellce are found 

 in sponges. The species of placuna, vulgarly 

 called the saddle oyster, is much sought after on 

 account of its form ; our specimen is of an ex- 

 traordinary size. The anomice are particularly 

 remarkable for the hole at the extremity of 

 their lower valve, from whence issues the pe- 

 dicle with which the animal fixes itself on the 

 rocks. 



6th. The six genera which compose the family 



