THE DUCKBILL. 201 



could endure below the surface of the water without 

 requiring to breathe was a little more than seven 

 minutes. Some specimens which he had in captivity, 

 used to sink to the bottom, and lie there quietly, 

 their position being only indicated by a bubble of air 

 rising occasionally to the surface. After a time they 

 would gradually rise in the water, just protruding 

 their nostrils for a few seconds, and again sink to the 

 bottom. Sometimes they float almost entirely im- 

 mersed, only the part of the beak containing the 

 nostrils being left out of the water. Under these 

 circumstances, the nostrils are often annoyed by 

 floating dust, or other substances ; and, if they cannot 

 be cleared off by a sharp ejection of the breath, the 

 bill is carefully washed. 



At the base of the beak there is a fold of skin, of 

 which Dr. Bennett writes as follows : 



" The use of the fold or lappet which falls back 

 over the fore part of the head and throat, may be to 

 prevent the mud, into which these creatures thrust their 

 beak, from injuring the surrounding fur; or, what is 

 more probable, protect the eyes from injury during 

 the time that they are burrowing in the earth. The 

 nostrils are situated at the upper surface of the beak, 

 near its extremity. 



" The formation of the lips enables the animal to 

 strain the water from its food, which is then conveyed 

 into two rather capacious cheek-pouches. As regards 

 the use of these, Professor Owen observes that any ' air- 

 breathing, warm-blooded animal, which obtains its 

 food by the capture of small aquatic animals while 

 submerged, must derive great advantage from the 



