HABITS OF RAZOR-FISH. 69 



together, at one side, into a short tube. On cutting a 

 little deeper we perceive that the shell is held together 

 by two muscles, one placed on each side of the central 

 hinge. The hinge itself is differently formed, the liga- 

 ment which connects the valves being external, and the 

 joint furnished with a nicely-fitted apparatus of tooth- 

 like plates. On the whole, we have a higher type of 

 structure, while the development of a large muscular 

 foot, capable of being either wholly retracted within the 

 shell or protruded to a considerable length, marks a 

 new feature in the animal, which at once suggests a 

 difference in habits and destiny. That the differences 

 observed in the organization of the Cockle, and of the 

 allied genera, Mactra, Venus, &c., and which are found 

 in a still more advanced state in the Myce or Gapers, 

 and the Solen or Razor-shell, admirably fit them for 

 the sphere of life for which they are designed, is at 

 once obvious when we consider these modifications of 

 structure in reference to the habitat of the animal. 

 All these animals inhabit sandy or muddy places. 

 Their dead shells are among the commonest which we 

 meet with on almost every strand ; and they may be 

 found in a living state, near low-water mark, buried in 

 holes, which reveal themselves by slight depressions, 

 from which little jets of sand and water may, every now 

 and then, be seen to issue. For such a life as this their 

 organization peculiarly fits them. Were their mantle 

 open on all sides, like that of the Scallop, their branchiae 

 would soon become choked with the sand or mud, which 

 would have free entrance with the water received into 

 the shell, and thus the animal would quickly be suffo- 



