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 Pandoridce 

 inhabit sand at various depths. 



Genus I. PANDO'BA*, Hwass. PL 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 : palps 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 : pallial scar 

 pitted at intervals : muscular 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 inaequivalvis, Linne) as the type. This is clearly 

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

 was published between two and three years before the 

 ' Encyclopedic Methodique/ Carpenter has remarked 

 the complete conformity that exists between the shells of 

 the present genus and Avicula, 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 ; 

 and in the truly nacreous interior. The genus appears 

 to be of comparatively recent origin ; for (according to 



* A mythological character. 



