FAMILY 3. AVICULACEA. 147 



Examples. 



PI. CVI, Fig. 1. 



Perna Isognomum, Lamarck, Anim. sans vert., new edit., vol. vii. p. 75. 

 Enc. Meth., pi. 176. f. 1. 



Ostrea Isognomum, Linnaeus. 

 Perna femor alis, De Blainville. 



PI. CVI. Fig. 2. 



Perna ephippium, Lamarck, Anim. sans vert., new edit., vol. vii. p. 74. 



Enc. Meth., pi. 176. f. 2. 

 Ostrea ephippium,, Linnaeus. 



MALLEUS, Lamarck. 



Testa irregularis, deformis, subaequivalvis, ut plurimum elongata, ad 

 basem saepissime utrinque lobata ; lobis rectis, umbonibus divari- 

 catis. Cardo edentulus, ligamento partim externo in area, declivi 

 utriusque valvae, partim interno in fossula trigona, centrali. La- 

 cuna pro bysso in valva. inferiori pone cardinem posita. Impressio 

 muscularis composita. 



When Bruguiere dispersed the Linnaean Ostrea, the Mallei or Hammer 

 Oysters were included amongst those which he proposed to associate 

 under the generic title of Avicula. They were afterwards set apart by 

 Lamarck for the formation of the present genus ; and the appellation of 

 Malleus was selected on account of the lateral lobes at the base of the 

 shell giving it the appearance of an inverted hammer. This, however, 

 only refers to the type of the genus ; Linnaeus introduced the word mal- 

 leus as a specific name, and in reference only to this particular species. It 

 must not be supposed that Lamarck founded his new genus entirely upon 

 the structure which its name implies, as there are one or two species of 



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