268 SUMMER 



and on the uncovered rocks also include a wonderful diversity 

 of snail-like univalves cousins of the inland snails of fields 

 and streams. Their spirals are moulded in almost infinite 

 variety. Even the whelk and periwinkle of the fish-market 

 show a considerable diversity ; the whelk belongs to the 

 more elongated spirals, and the periwinkle to the rounder. 

 Extremely contrasted forms are provided by the long pointed 

 turritella shells, which look like the trumpets of sea-fairies, 

 and the bright yellow houses of the sea-snail, in which the 

 spiral outline is compressed to the smoothness of a pebble. 

 One striking point of difference as compared with inland 

 types is the thickness of most of these shells. To resist the 

 beating of the waves they need far greater strength than 

 the snails which dwell on land, or in the more even current 

 of rivers. Inland snails have coats like egg-shells, but most 

 sea-snails are defended like the kernel of a nut. 



Yet not only the hard shell of the molluscs, but the rocks 

 themselves, yield to the fret of other shells, and some of 

 them among the frailest of their kind. Single shells of 

 oyster or mussel or other bivalves are often found pierced 

 with a neat round hole, as if meant for threading into 

 children's necklaces. This is the work of the dog-whelk. 

 The dog-whelk is a small species of whelk it is reputed 

 to be poisonous with a thick smooth shell, which is often 

 found prowling alive on stones and in pools. It is one 

 of the predatory species of the beach, hunting for the 

 bivalves which are apparently so safely sealed in their 

 double shells. The dog- whelk sits on one of the shells near 

 the hinge, and bores a hole to the fish inside. It thus 

 paralyses the muscles which contract the shells, and when 

 they gape open enters and feeds upon the occupant. To 

 open an oyster is a sufficiently remarkable feat for a whelk 

 not half as large as a common garden-snail. But shell-fish 



