PHOLADOMYA. 363 



very peculiar arrangement of the epidermis. In the middle 

 of the shell it lies in ridges parallel with the lines of growth, 

 but towards the ends, especially the anterior, it turns sud- 

 denly upwards, and becomes dispersed in scattered shrivelled 

 wrinkles. 



noladomyay concerning which little at present is dis- 

 covered, is, however, arranged with the Solenacea. The shell 

 is tliin, rather hyaline, transverse, ventricose, pearly in the 

 inside; posterior side sometimes very short, rounded; an- 

 terior side more or less elongated, gaping ; upper edge also 

 gaping a little. Hinge with a small, rather elongated, 

 triangular pit, and a marginal lamina in each valve, to the 

 outer part of which is attached the somewhat short external 

 ligament. Muscular impressions, two : these, equally with 

 the muscular impression of the mantle, in which there is a 

 large sinus, are indistinct. 



Shells, in their endless diversity, present an inexhaustible 

 fund for contemplation and delight. Select two shells of 

 the same species, as much alike as possible, both in form 

 and colour, and place them side by side. At first, perhaps, 

 you see no difference. Look again, and you will observe that 

 no two spots, nor bands, nor lines, nor tintings are exactly 

 similar ; and when you consider the number of shells that 



