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ation was rather light so that against the sand bottom they were 

 very inconspicuous. At times their shadows were more visible 

 than the owners. Most interesting was their ability to stop 

 instantly in their flight. I never quite discovered how it was 

 managed. Their pectorals were spread apart as checks or brakes 

 but not to the extent it seemed necessary to halt a hundred 

 pounds of gliding fish. They could also make a complete re- 

 versal within their own length, though I only saw this done 

 once. Usually they banked steeply, rolling slightly to one side 

 and then came about in a long graceful sweep. 



By way of entertainment I gathered a group of prickly sea 

 urchins from some rocks near shore and carried them under me 

 along with a five-pronged spear. With this instrument I crushed 

 several and rolled them along the bottom. Then I retired twenty 

 or thirty feet away. For a long time I waited. Nothing hap- 

 pened except that in the meantime a group of small fish began 

 tearing at the broken urchins and soon had them all eaten up. 

 I gathered some more which I beat into an oozy pulp with a 

 rock. This time I had better luck although hardly ten seconds 

 had elapsed before the bait was surrounded by a dense cloud of 

 fish. There was no shooing them away so I withdrew, hoping 

 against hope that my bait would last until the nurses got the 

 scent. They did. A few seconds later I saw their shapes devolv- 

 ing out of the blue sunlit haze. They were no longer moving 

 leisurely but were sweeping along at considerable speed al- 

 though they did not give the impression of being in a rush. 

 One approached directly head on and I was interested to ob- 

 serve that it did not move in a straight line but was weaving 

 from side to side. Apparently its sense of direction was dictated 

 by the use of alternate nostrils. When it received the strongest 

 stimulation on one side it swung in an arc until the other was 

 affected. As soon as it saw the bait the weaving ceased. With a 

 rush it swept up with its companion, glided over the urchins, 



