528 aviculidjE. 



shells are like Aviculce, but during the growth of the animal 

 layers are developed from the edge of the valves until the 

 shell assumes the peculiar elou gated form from which it 

 derives its familiar name of the " Hammer Oyster." The 

 species are found in the Indian and Chinese seas. 



Species of Malleus. 



albus, Chem. normalis, Lam. 



decurtatus, Lam. regula, Forsk. 



figuratus, Chem. vulgaris, Lam. 



Genus CRENATULA, Lamarck. 



Shell equivalve, thin, oblong, compressed, lamellated, 

 rather irregular; byssal sinus obsolete. Hinge lateral, 

 linear, marginal, with numerous shallow, crescent-shaped 

 cartilage-pits. 



Syn. Dalacia, Gray. 



Ex. C. semiaurata, Gmelin, pi. 123, fig. 3, 3, a. 



The species of Crenatula appear to want the usual 

 byssus seen in genera of this family, and to take up their 

 abode in sponges. They are found in the seas of India, 

 Australia, North Africa, China, and in the Red Sea. 



Species of Crenatula. 



bicostalis, Lam. pergaminea, Gould. 



modiolaris, Lam. picta, Gmel. 



mytiloides, Lam. semiaurata, Gmel. 



nigrina, Lam. viridis, Lam. 



