98 Shell Life 



prominent, and the ridges somewhat overlapping, 

 tlieir terminations giving a spiny character to the 

 upper margin. There is but one cardinal tooth in the 

 right valve, but in the left there is a small additional 

 one. It is more plentiful on our northern shores than 

 in the south, and especially on the west coast of 

 Scotland. 



In the next genus, the Hatchet-shells {Aximis\ the 

 smooth shell is more globular, though with a triangular 

 outline, the hinder portion furrowed. The beaks are 

 considerably recurved, but the hinge-teeth are entirely 

 wanting, though an excavation in the right valve and 

 a corresponding eminence in the left have somewhat 

 the appearance of teeth. The margins of the shell 

 are not toothed. The thickened margin of the mantle 

 is open all round and not prolonged into siphons. 

 The long slender foot is almost cylindrical. There 

 are five British species, all small and all living on 

 muddy - sandy shores. The Rusty Hatchet - shell 

 (^. ferruginosns) is the most plentiful of these, 

 and gets its name from a rust-like deposit over the 

 epidermis which protects the thin, white, almost 

 globular, shell. It occurs between 30 and 100 fathoms, 

 chiefly oflf Skj^e, Shetland, and the west of Ireland. 

 The Wavy Hatchet-shell {A. flexuosiis) has a more 

 oval and less glossy shell. The terms " wav}^ " and 

 "flexiLOSiis" apply to the upper margin behind the 

 beaks. The hinder margin of the mantle is con- 

 tracted so as to form some approach to a siphon or 

 the aperture of one. This species is widely distri- 

 buted, and ranges between 3 and 90 fathoms. The 

 Skye Hatchet - shell (A. crouUnensis) is obliquely 

 oval, swollen, more solid, and longer than the last 



