NATURAL TllEOLOGV. 233 



But tlie species of bii). which belongs to the 

 birds that live by suction deserves to be described 

 in its relation to that office. They are what na- 

 turalists call serrated or deiitated bills ; the inside 

 of them, towards the edge, behig thickly set with 

 parallel or concentric rows of short, strong, sharp- 



the same advantage that we have when we put a nut nearer the 

 joint of the nut-cracker, that is, nearer the fulcrum. 



One disadvantage of this form and shortness of the bill would 

 be, that the mandibles could not open wide enough to take in a 

 large seed ; but it is provided that the upper mandible shall move 

 upon the skull as well as the lower one, a subject which has not 

 escaped our author's attention. 



The form of the bill of the cross-biil, which he mentions, looks 

 like an imperfection, but is attended with real advantages. It is 

 not for crushing, but rather for splitting up a seed into halves and 

 tearing tlie cones of the fir-tree. 



One of the most curious provisions is in the bill of the sea-crow. 

 The mandibles are compressed into the form of simple laminae, 

 and the lower mandible projects beyond the upper one ; so that, 

 as he skims along the water, he dips his bill and lifts his food by 

 the most appropriate instrument 



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