17 



TADORNA. SHIELDUCK. 



It may at first sight seem difficult to determine whether 

 our common Shielduck be actually a Duck at all, it having 

 very much of the appearance of a Goose ; and a close inspec- 

 tion rather increases than removes our perplexity. If we 

 refer to authorities, we find some on one side, and some on the 

 other. The bill, however, is decidedly that of a Duck, for 

 besides increasing in breadth toward the end, it has a small, 

 oblong unguis, not only smaller and differently formed from 

 that of any Goose, but moreover remarkably incurved at the 

 end ; and, although the genus approaches to Chenalopex 

 both in form and colouring, I think we may safely place it in 

 the group of Anatinge, assigning it tliere a station indicative 

 of its approximation to the Anserina?. The body is large, 

 full, rather elongated, about the same height and breadth ; 

 the neck rather long and slender ; the head moderate, oblong, 

 compressed, and rounded above. 



Bill as long as the head, higher than broad at the base, 

 gradually depressed, becoming a little broader toward the 

 end, and considerably rearcuate ; upper mandible Avith the 

 lateral sinuses semicircular, the upper occupied by a fleshy 

 knob, the dorsal line sloping to beyond the nostrils, then a 

 little concave ; the ridge flattened and gradually narrowed, 

 the unguis oblong, rather abruptly bent downwards and 

 inwards, with the end sharp-edged and abrupt, the sides con- 

 vex, at the base nearly erect, the edges rearcuate, the lamellae 

 with their outer ends thin and not appearing beyond the 

 margin, which is somewhat expanded and membranous about 

 a third from the end ; the nasal sinus moderate, elliptical, 

 close to the ridge ; lower mandible considerably rearcuate, 

 with the intercrural space \ery long, narrow, and bare, the 

 crura slender, with their sides convex, gradually sloping more 

 outwards, the unguis somewhat elliptical, larger than the 

 upper, little convex, broadly rounded at the end. 



Mouth rather narrow ; anterior palate concave, Avith a 

 median prominent line, and on each side a series of trans- 



VOT,. V. c 



