52 THE ZOOLOGIST. 



spot. In a few of the naturally treated shells, several or many 

 bulbs were present. In some, longitudinal or oblique scratches 

 or grooves were visible on the lower surface of the last whorl, 

 and usually had associated with them a diffusely abraded area 

 on the lower surface of the second last whorl. These scratches 

 cannot be reproduced by simple longitudinal or obliquely inclined 

 rolling of the shells under pressure. It is necessary, in addition, 

 to impart a small amount of bodily movement to the shells in 

 the direction of pressure. 



Patella vulgata. 



According to Robert Gray,* the Oystercatcher inspects the 

 Limpets one after another, in order to see whether or not the 

 shells are at all raised from the rock. On meeting such a one 

 the bird promptly pushes its bill under the Limpet, and neatly 

 turns it over. One foot is then placed on the shell, and the body 

 of the animal is " taken out as cleanly as if done with a knife or 

 other sharp instrument." 



When the Oystercatcher is about to overturn a Limpet it 

 lowers its head and inclines the bill at a low angle towards the 

 ground, the attitude and purpose of the bird being similar to 

 those of a battering-ram in action. For a reason which I shall 

 explain immediately, the bill is directed downwards and forwards, 

 with its sides at right angles to the plane of the ground. In this 

 peculiar attitude the Oystercatcher delivers a sharp push or 

 chipping stroke to a portion of the edge of the selected Limpet. 

 With a small Limpet the stroke, if successful, shifts the animal 

 bodily from its seat. The advancing edge of the shell catches in 

 some obstruction, and the shell topples over. With larger 

 shells the stroke has usually to be followed up by firm and 

 evidently laborious pushing, assisted, it may be, by swaying of 

 the bill from side to side, with finally a raising of the head and 

 the bill, or a to and fro rotation of the bill through barely a 

 quarter of a circle. In these larger shells the bill is obviously 

 forced under the animal, and the process of overturning is 

 usually completed by means of some more patent form of 

 leverage. The Limpet is then seized and carried by the flesh, 

 the edge of the shell, or by being held in the line of its breadth 



■ Birds of the West of Scotland,' p. 270. 



