BIVALVES AND CUTTLES. 283 



The first genus the old maid shells, or Myas includes 

 two common species which live buried in sand near low- 

 water mark, and often occur in large numbers on the beach 

 after storms ; the empty shells are to be found at all seasons. 

 In both the siphons are large, invested in a common sheath, 

 and united throughout their length. The shell is oval or 

 oblong, and gapes at both ends. The hinge -cartilage is 

 wholly internal, and is placed between a cavity in the right 

 valve and a hollow in a conspicuous process of the left 

 valve. The internal position of the cartilage and the 

 presence of the large cartilage in the left valve make the 

 shell of a Mya easily recognised. The shells are solid, 

 opaque, not glossy, and with little brightness of tint. The 



FIG. 81. Mya truncata, showing siphons and foot. 



two species are Mya arenaria and Mya truncata, chiefly 

 distinguished by the shape of the shells. In M. arenaria 

 this is oblong, and about twice as long as broad; in 

 M. truncata it is oval, and the length bears to the breadth 

 about the proportion of five to four. In the latter, further, 

 the posterior end of the shell is abruptly truncated ; in the 

 former it is wedge-shaped. Both are used as food and bait, 

 and are greatly relished by seagulls, who may be found 

 feasting on them after storms. 



The other genus includes the otter-shells (Lutraria), of 

 which we have one common species, L. ettiptica, which 

 inhabits the same localities as the Myas, and is to be found 

 with these after storms on the shore. The siphons are very 

 long, and are inclosed in a common sheath, but are not 

 completely united. As in Mya, the shell gapes at both 

 ends, but it is much thinner, and is glossy and brightly 

 coloured. The shape is elliptical and compressed, the car- 



