238 ORIGIN OF SPECIES 



the head of the shoveller as long as that of the Balsenoptera, 

 the lamellae would be six inches in length, — that is, two-thirds 

 of the length of the baleen in this species of whale. The 

 lower mandible of the shoveller-duck is furnished with 

 lamellae of equal length with those above, but finer; and in 

 being thus furnished it differs conspicuously from the lower 

 jaw of a whale, which is destitute of baleen. On the other 

 hand, the extremities of these lower lamellae are frayed into 

 fine bristly points, so that they thus curiously resemble the 

 plates of baleen. In the genus Prion, a member of the dis- 

 tinct family of the Petrels, the upper mandible alone is fur- 

 nished with lamellae, which are well developed and project 

 beneath the margin; so that the beak of this bird resembles 

 in this respect the mouth of a whak. 



From the highly developed structure of the shoveller's 

 beak we may proceed (as I have learnt from information and 

 specimens sent to me by Mr. Salvin), without any great 

 break, as far as fitness for sifting is concerned, through the 

 beak of the Merganetta armata, and in some respects through 

 that of the Aix sponsa, to the beak of the common duck. 

 In this latter species, the lamellae are much coarser than 

 in the shoveller, and are firmly attached to the sides of the 

 mandible ; they are only about 50 in number on each side, and 

 do not project at all beneath the margin. They are square- 

 topped, and are edged with translucent hardish tissue, as if 

 for crushing food. The edges of the lower mandible are 

 crossed by numerous fine ridges, which project very little. 

 Although the beak is thus very inferior as a sifter to that 

 of the shoveller, yet this bird, as every one knows, constantly 

 uses it for this purpose. There are other species, as I hear 

 from Mr. Salvin, in which the lamellae are considerably less 

 developed than in the common duck; but I do not know 

 whether they use their beaks for sifting the water. 



Turning to another group of the same family. In the 

 Egyptian goose (Chenalopex) the beak closely resembles that 

 of the common duck; but the lamellae are not so numerous, 

 nor so distinct from each other, nor do they project so much 

 inwards ; yet this goose, as I am informed by Mr. E. Bartlett, 

 "uses its bill like a duck by throwing the waters out at the 

 corners." Its chief food, however, is grass, which it crops 



