OBSERVATIONS ON THE OYSTEBCATCHEB. 47 



together, and, as a rule, they are well hidden amongst vegeta- 

 tion, or in the sandy concretions of diverse materials that clothe 

 the rocks in many places. In consequence, the search for 

 Modiola takes the form of a close and extensive inspection, with 

 frequent, vigorous probing into the concretions in selected spots. 

 The shells are entered and opened up precisely as if they were 

 those of the Edible Mussel. But in the majority of cases they 

 are dragged from their anchorage before being levered widely 

 open and cleared of their contents. This difference is no doubt 

 due to the difficulty which would be experienced in separating 

 the valves amongst matted vegetation or miscellaneous concre- 

 tions. After detaching the shell, the Oystercatcher selects some 

 kind of support, such as a crevice in the rock, on which to rest 

 the shell before levering it open. A support is the more neces- 

 sary when the shell has been entered through the hiatus in the 

 ventral border, owing to the rounded form of the dorsal surface. 

 For a similar reason nesting is occasionally employed. 



The shells vary in size from two and a quarter inches in 

 length by one and a quarter inches in breadth (2| in. x 1£ in.) 

 to nine-sixteenths of an inch in length by five-sixteenths of an 

 inch in breadth (^ x T 5 6 ), the average size of a hundred shells 

 being one and three-sixteenths inches by five-eighths of an inch 

 0-i 3 6 x f)- The3e hundred shells include eleven which were 

 opened by the hammering method. Of the eleven, the largest 

 measures one and a quarter inches by five-eighths of an inch 

 (1J in. x § in.), and the smallest as given above, the average 

 size being fifteen-sixteenths of an inch by seven-sixteenths of an 

 inch (]■% in. x T 7 g in.). The smallest shell opened by the 

 thrusting method measures five-eighths of a inch by three- 

 eighths of an inch (f in. x f in.). The biggest shell of the 

 whole series is exceptionally large. It had been entered through 

 the hiatus in the ventral border, and was uninjured. Of the 

 hundred shells, sixty-four were entered via the ventral border, 

 six through the posterior end, and thirty by the dorsal border. 

 These figures roughly reverse the percentages obtained from 

 Mytilus eclulis. The cause, as in the latter case, is to be found 

 in the natural position of the shells. In Modiola the habit of 

 living more or less hidden under vegetation and other cover 

 allows, apparently, of the assumption of various attitudes, and, 



