OBSERVATIONS ON THE OYSTERCATCHEJR. 53 



within the tips of the mandibles. It is deposited in a suitable 

 crevice of the rock or on sand, and the contents are separated 

 from the shell by chipping through the friable attachments of 

 the mollusc to the internal surface of the shell, the process of 

 detachment often being completed by the bird shaking its bill, 

 and flicking the shell off the body of the mollusc as the head 

 is raised. 



The shells vary from one and three-quarter inches in length 

 by one and a half inches in breadth (If in. X 1± in.), to half 

 an inch in length by seven- sixteenths of an inch in breadth 

 (£ in. x T 7 g in.), the average size of one hundred and thirty-four 

 shells being seven-eighths of an inch by eleven-sixteenths of an 

 inch (|- in. x 11 in.). Out of one hundred and sixty-one shells, 

 85 per cent, are whole, or at most only abraded at one part of 

 the margin of the shell, and 15 per cent, are fractured. In the 

 series the occurrence of abrasion and fracture has no visible 

 relation to the size of the Limpet, and no recognisable rule of 

 position in relation to the margin of the shell. The fracture 

 may be a small V-shaped chip out of the edge of the shell, a 

 larger quadrangular fragment, or, as in a few cases, it may be 

 semi-annular. The shells are invariably well cleaned. They are 

 carried in about equal numbers to crevices in the rock and to 

 sand for the purpose of removing the contents. In no case was 

 a footmark impressed on the sand so as to overlap the shell, or 

 its mark if the shell had been flicked away. In each case a wide 

 gap separated the shell or its impress from the corresponding 

 footprints. This agrees with my observations. I have not as 

 yet been able to detect an Oystercatcher in the act of steadying 

 a shell with one of its feet. On rock, evidence of equal value 

 cannot be adduced, but some sort of support is of invariable 

 occurrence in order to render the shells stable during the 

 removal of their contents. Usually it takes the form of a crack 

 or depression in the rock. Further, nesting of the shells is 

 common for the same purpose, two, three, or four being piled 

 one on the top of another, in each case as a preliminary to the 

 extraction of the mollusc. On one occasion I found a nest of 

 five Tapes and three Limpets in that order from below upwards. 

 After going over the evidence derived from direct observa- 

 tions, and from an examination of the shells, I feel there are at 



