SHORES OF THE CLYDE AND FIRTH. 
67 
the particles away, and always keep the passages free from 
obstruction. 
In the observation of this interesting operation, the 
first thing we see is a settling down process, then gradually 
a little ring of sand gathers round the outer edges, which 
continues to enlarge until half the creature is buried, and 
when it is finally out of sight, all trace of its whereabouts is 
gone; but when deep enough the two breathing vents appear, 
which sometimes run into one when the tide leaves them 
bare. 
The sucker arms and pedicellariae of this species are not 
so numerous as in the case of the other The former 
protrude or pierce the thin fragile shell in the form of a 
four-pointed star-fish, and possibly this is the reason why 
some writers have suggested the idea of a connection with 
the star-fish families. 
THE COCKLE. 
Amongst the numerous little punctures in the sands, 
indications of life below, we find another double vent, but 
the size is much less than that of the urchin ; and here it is 
at our toe, the abode of the cardium edule or common cockle. 
No shellfish is better known than the cockle. The denizens 
of the streets and lanes of our crowded inland towns who 
have never seen the sea are quite familiar with its appear- 
ance, and very few sandy stretches on the estuaries and 
bays of our northern coast but contained them in more or less 
abundance. The Rev. J. G.Wood, in his " Common Objects 
of the Sea Shore," in speaking of the cockle says : ''The 
cockle is a capital delver, and armed with his natural spade 
digs for himself a hole in the sand nearly as fast as a man 
can dig with a spade of metal." Philip Henry Gosse again 
speaks of it in this fashion: "Like all the rest of its 
