ANSERES 113 



membrane, except at the tip of the upper mandible, where there is 

 a hard nail ; furthermore, both mandibles have just inside their 

 cutting edges a series of horny lamellae of varying development in 

 different genera ; the number of tail feathers varies from fourteen to 

 twenty-four ; the legs are short and the anterior toes fully webbed ; 

 the hind toe is small and jointed above the level of the others ; the 

 eggs are numerous, white, pale greenish or creamy, and un- 

 spotted ; the young are covered with down when hatched, and able 

 to run or swim at once. 



Anatomical characters are : skull desmognathous and holorhinal ; 

 basipterygoid facets present; after -shaft small or absent; two 

 carotids ; syrinx with two pairs of intrinsic muscles, and often 

 with a bony or membranous enlargement ; oil gland tufted ; caeca 

 long ; all the garrodian thigh muscles present except the accessory 

 semitendinosus. 



There is only a single family of this Order in South Africa, and 

 this again it is by no means easy to divide into sub-families ; the 

 Swans, true Geese and Smews can perhaps be satisfactorily dia- 

 gnosed, but all the genera represented in South Africa seem to fall 

 within the limits of the typical subfamily Anatince. 



Key of the Genera. 



A. Hind toe not lobed or very narrowly lobed ; its 

 breadth never one-third the length of the toe. 



a. No metallic speculum on the wings. 



a 1 . Tarsus with a line of transverse scutes in 



front. 

 a 2 . Size very large, wing over 20 ; face bare ; 



a strong carpal spur Plectropterus, p. 114. 



b 3 . Size moderate, wing about 14 ; face 

 feathered ; a comb -like elevation on the 



bill of the male Sarddiornis, p. 118. 



c 2 . Size very small, wing about 6 ; bill short 



and deep; no spur or comb Nettopiis, p. 121. 



b l . Tarsus reticulate throughout ; bill with a 



strong nail directed vertically downwards Dendrocycna, p. 124. 



b. A metallic or brightly coloured speculum on 



the wings formed by the outer secondaries. 

 a. 1 . Bill about equally broad throughout its 

 length. 



8 VOL. IV. 



