20 



Mr. Swainson on the Typical Perfection 



striking characteristic, therefore, of the genus we are now 

 considering has nearly disappeared, precisely in that form 

 which is furthest removed from the type. But the shape of 

 the bill, although essentially modified, has not undergone a 

 total alteration : its breadth towards the tip is not only as great 

 as at the base, but is even more dilated ; so that, in this respect, 

 it resembles the Shovellers more than the Gadwalls, while it 

 differs from both in being higher at its base, considerably more 

 lengthened in proportion, and much more convex throughout. 



It assumes, in short, a semi-cylindrical form, the end being 

 particularly obtuse and slightly dilated. The precise point of 

 junction between the Pin-tails and that group which was 

 known to the ancients by the name of 



BOSCHAS, 



has not yet been explained. Under this subgenus we compre- 

 hend all those ducks usually denominated Teals, together with 

 the Mallard, long domesticated in our poultry yards. As this 

 is by far the most numerous group, so it exhibits a greater 

 diversity of form among the species. They are all, however, 

 characterised by a bill longer than the head, whose breadth is 

 equal throughout ; it is sometimes, indeed, a little dilated, but 

 never contracted at its tip, while the laminaB of the upper man- 

 dible are entirely concealed by the margin of the bill. The 

 neck and the tail, which in Dafila are both considerably length- 

 ened, are much shorter in this group, which is further distin- 



