ORNITHOLOGICAL EXPLORATIONS. 



167 



cates more plainly that the Harlequin Duck is misplaced iu all of them, 

 and Histrionicus, iu fact, is oue of the best marked genera iu the whole 

 group. Besides all the other characters, it has a peculiarity of its owu, 

 which at once distinguishes it from all others of its kind, the soft, naked 

 membrane at the base of the upper mandible overlapping the tomium 

 and concealing the corner of the month and the base of the lower man- 

 dible for a distance of not less than 9"'"'. 



This membri'.ue shrinks considerably when the skin is prepared and 

 dried. The true size and structure of the nostrils and many other parts 

 of the bill are usually distorted in museum S])ecimeus. I, therefore 

 wrote down a synoptical comparison of the bills of Histrionicus minutus 

 and Rarelda hyemalis, with the fresh specimens before me which I 

 think it may be of some interest to reproduce ; the notes are as follows : 



HareJda. Histrionicus. 



Niiil of upper uuiudible distiuct, vault- Nail of upper inaudible iudistiuct, flat, 

 cd, narrower than tlie bill. occupying- tlie whole breadth of the bill. 



Tomia of upper mandible bent upwards 

 toward the tip. 



Lamelhe of upper mandible few, dis- 

 tant, and,, in the hind part of the commis- 

 sure, long, pendant, and visible below the 

 toniiuni. 



Edges of nostrils not swollen or raised 

 above the surface of the bill. 



Base of upper mandible without over- 

 hanging membrane. 



Upper mandible of equal breadth to 

 a point beyond the nostrils. 



Frontal feathering proceeds farther on 

 the bill, almost as far as the hind border 

 of the nostrils, the mesial apex being 

 rounded and the lateral border with a 

 prominent but obtuse angle above, while 

 concave below. 



Lower mandible with a distinct "nail." 



Lamelhe of the lower jaw few, distant, 

 and very prominent, distinctly visible 

 outside of the tomia when viewed from 

 below. 



Lateral outlines of lower jaw, viewed 

 from below, decidedly curved inward. 



Length of symi>hysis less than the 

 breadth of the lower jaw at the hind 

 border of the symphysis. 



Feathering on mental angle pointed 

 anteriorly. 



Distance from mental feathering to tip 

 of lower jaw less than from the former to 

 corner of mouth. 



Tomia of upper mandible straight to 

 the tip. 



Lamelhe of upper nmndible numerous, 

 close together, and not visible below the 

 tomium. 



Edges of nostrils swollen, raised above 

 the surface of the bill. 



Base of upper mandible with a soft, 

 naked membrane overlapping the tomium. 



Upper inaudible diminishing in breadth 

 gradually from the base. 



Frontal feathering does not i^roceed so 

 far on the bill as the hind border of the 

 nostrils; mesial apex pointed ; loral bor- 

 der convex. 



Lowermandible-withoutdistiucfnail." 

 Lamelhe of lower jaw numerous, close 

 together, and hardly perceptible outside 

 of the tomia when viewed from below. 



Lateral outlines of lower jaw, viewed 

 from below, straight, converging grad- 

 ually from the base. 



Length of symphysis greater than the 

 breadth of the lower jaw at the hind bor- 

 der of the symphysis. 



Feathering on mejital angle rounded 

 anteriorly. 



Distance from mental feathering to tip 

 of lower jaw much greater than from the 

 former to corner of mouth. 



