756 U. S. p. R. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



Family ANATIDAE. 



Ch.— The two jaws with transverse lamellae, alternating and fitting in each other. Upper mandible ending in an obtuse, 

 rounded nail. A groove*unning along both jaws to the nail. The feathers of the forehead extend forward on the culmen in a 

 rounded or acute outline ; those on the side of lower jaw and on the chin extend forward in a similar manner. Commissure 

 straight. Legs short. 



The Anatidae, or the family of the ducks, are universally distributed throughout the globe, 

 and embrace an unusual proportion of species inhabiting both the Old and New World. The 

 sub-families are all represented in North America, and a large number of the genera also. 

 The sub-families are as follows : 



A. The teeth of the bill directed downwards, the lamellae composing one series only 

 On the edge of the upper jaw. The rami of the lower jaw separated. Bill broad ; depressed 

 at the end. 



a. Tarsi reticulated, covered anteriorly with small hexagonal plates, gradually becoming 

 smaller and rhomboidal laterally. Hind toe without free lobe. 



Cygninae. — Neck very long. Bill high at the base ; longer than the head ; of 

 eq^ual width to the rounded tip, with its narrow nail. Soft skin of bill generally 

 extending to the eye. Tarsi shorter than the middle toe without claw. 



Anserinab. — Neck rather long. Bill high at base ; as long as or shorter than 

 the head, narrowing to the tip, which is chiefly formed by the large nail. 

 Kegion in front of the eye feathered. Tarsi longer than middle toe without 

 claw. 



b. Legs with transverse plates or scutellae anteriorly, these becoming much smaller and 

 more hexagonal laterally and behind. Tarsi generally shorter than middle toe without 

 claw ; sometimes only half as long. 



Anatinae. — Hind toe without a broad membranous lobe attached. Tarsi not 



longer than the middle toe ; feet moderate. 

 FuiiGULiNAE. — Hind toe with a broad membranous lobe depending from its under 

 surface. Feet large. Nail of bill superior, gently decurved. Tail rather soft ; 

 the coverts well developed. 

 Erismaturinae. — Toes and feet as in the last. Nail of bill abruptly bent back 

 from tip of bill, showing but little on upper surface of the latter. Tail feathers 

 rigid, spinous, and almost entirely exposed ; the coverts much abbreviated. 

 B. Bill high at the base, much compressed. The lamellae directed backwards as serrations. 

 The upper jaw with two series of teeth on each side ; the lower with one which fits between 

 the others. The nail of the bill compressed^ much curved, forming the tip of the bill. Edges 

 of bill nearly parallel. Legs with transverse plates anteriorly. 

 Merginae. — Characters as above. 



