ANSERES CASARCA 131 



Genus VI. CASARCA. 



Type. 

 Casarca, Bp., Comp. List, p. 56 (1838) C. rutila. 



Bill rather short, high at the base but with a nearly straight 

 culmen and about the same breadth throughout ; lamellae at the 

 edges of both mandibles prominent and conspicuous ; nail small 

 and blunt ; wings long and pointed, first primary the longest, a 

 conspicuous speculum, formed by the outer webs of the secondaries ; 

 an osseous callosity at the bend of the wing ; tail of fourteen 

 feathers, short and nearly square ; tarsus about equal to the middle 

 toe and claw, covered with reticulate scales, those along the middle 

 line in front on the lower half slightly broader than the others, and 

 forming a transverse row of scutes ; hind toe with a very narrow 

 lobe ; prevailing coloration chestnut ; sexes dissimilar. 



This genus, containing the Sheldrakes or Shelducks, consists 

 of four species, and is spread all over the Old World, including 

 Australia. One species only is found in South Africa, though the 

 Euddy Sheldrake (C. rutila) comes as far south as Abyssinia during 

 the northern winter. 



618. Casarca cana. South African Slielduck. 



Gray-headed Duck, Brown, New Illustr. Zool pp. 802, 104, pis. 41-2 



(1776). 



Anas cana, GmeL, Syst. Nat. i, p. 510 (1788). 

 Casarca cana, P. L. Sclatcr, P. Z. S. 1859, p. 442, pi. clviii. (hybrid with 



Tadorna cornuta) ; Gurney, Ibis, 1868, p. 262 ; Ayres, Ibis, 1871, 



p. 266, 1885, p. 350 ; Sli-arpe, ed. Layard's B. S. Afr. p. 753 (1884) ; 



Symonds, Ibis, 1887, p. 335 ; Nicolls and Eglington, Sportsm. S. Afr. 



p. 129 (1892) ; SaJvadori, Cat. B. M. xxvii, p. 182 (1895) ; Shelley, 



B. Afr. i, p. 171 (1896) ; Reiclienow, Vog. Afr. i, p. 137 (1900) ; 



Whitehead, Ibis, 1903, p. 237 ; Sharpe, Ibis, 1904, p. 17 [Deel- 



fontein] ; Shortridge, Ibis, 1904, p. 207. 

 Casarca rutila (nee Pall), Layard, B. S. Afr., p. 350 (1867). 

 " Berg-eend " of the Dutch. 



Description. Adult male. Head and neck all round dark ashy- 

 grey ; mantle, scapulars, outer webs of the inner secondaries and 

 lower parts throughout, rufous-chestnut, paler on the mantle, breast 

 and under tail-coverts; centre of the back, tail-coverts, tail, primaries 

 and primary-coverts black, the back vermiculated with rufous ; 

 outer secondaries metallic-green on the outer web, ashy-black 

 on the inner, with a good deal of white towards their bases ; wing- 



