PANDORA. 23 



The shape of the shell, its nacreous substance, and the 

 absence of an external ligament are the chief character- 

 istics that distinguish this small family. The two genera 

 which compose it have a different hinge- structure, but 

 are in other respects so closely allied, that it is more 

 convenient to place them together. The Pandorida 

 inhabit sand at various depths. 



Genus I. PANDO'RA*, Hwass. PI. I. f. 4. 



Body oval, compressed on one side and rather tumid on the 

 other, thin, and gelatinous : gills free, except at their bases, 

 where each pair is united, and terminating in the tubular 

 sheath : p>alps short : foot small, thick, and swollen at the 

 point. 



Shell oval, inequilateral, scaly and smooth ; left valve flat 

 and the other convex : epidermis membranous and thin : teeth 

 consisting of a plate-like cardinal in each valve : pallicd scar 

 pitted at intervals : muscxdar scars well marked, roundish-oval. 



The merit of instituting the genus Pandora is due to 

 Hwass, a German justiciary, and not to Bruguiere as is 

 commonly supposed. Both gave the same species (Tel- 

 Una buequivalvis, Linne) as the type. This is clearly 

 shown by the 11th volume of Chemnitz (p. 211), which 

 was published between two and three years before the 

 ? Encyclopedie Methodique/ Carpenter has remarked 

 the complete conformity that exists between the shells of 

 the present genus and Avicida, — namely, in the regular 

 prismatic arrangement of the cellular structure, the axes 

 of the prisms being perpendicular to the surface ; in the 

 presence of distinct partitions between the cells, forming 

 a persistent membrane, which is left after decalcification j 

 and in the truly nacreous interior. The genus appears 

 to be of comparatively recent origin; for (according to 



* A mythological character. 



