PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 175 



give the structural differences by which they are to be separated, so 

 that I find it not improbable that an exact investigation, based on a 

 more abundant material than I can at present procure, will reduce the 

 subfamilies to groups of lower rank. 



CHARACTERISTICS OF THE SUBFAMILY. 



External characters. 



N^eck very long, as long as, or longer than, the body. Bill longer 

 than the head, broad, and of nearly equal breadth for the whole length, 

 rounded at the end, culmen high, depressed at the tip; nad rather 

 large, only slightly arched; lamelhie of upper mandible vertical, in one 

 row; nostrils situated nearly at the middle of the bill, in the fore part 

 of the oblong nasal sinus. Lores naked in the adults ; iu all species, 

 except one, thinly covered with small down or feathers in the young. 

 Legs short, stout ; lower part of tibia naked; tarsi compressed, nuich 

 shorter than the middle toe with the claw, and covered with small hex- 

 agonal plates, the size of which diminishes laterally and posteriorly; the 

 anterior toes reticulate as far as the second joint, then scutellate; mid- 

 dle toe longest, longer than the tarsus, the outer longer than the inner, 

 which has a broad margin; hind toe short, elevated, and without web,* 

 the claws strong, arched, compressed except the middle, which is only 

 compressed on the one side, the claw of the inner toe in old birds the 

 largest and most arched. Wings long, ample, the inner remiges highly 

 developed, with about 32 quills. Tail composed of 20-24 rectrices, 

 short, rounded, or cuneate. 



Sexes similar. 



Os teo log tea I cha racters. 



The Swans, restricted as above, have a rather elongated skull, the 

 intermaxillar portion being especially lengthened, but their cranium 

 does not otherwise differ materially from that of the other Anati(la\ As 

 a rule, however, the Cyynhiw lack the two apertures on the occiput just 

 above the foramen tnarinum, which always are to be found in the other 

 members of the tiimilyt as well circumscribed and often large foramina. 

 The glandular depressions along the roof of the orbits are more or less 

 well marked. They are rather distinct in the genus Cygnus, whereas 

 they seem to be wanting in most of the other Anatidcc. 



The neck is extremely long, longer than the body, and is composed of 

 the greatest number of vertehrce yet discovered in any recent bird, viz, 



*Tliis expression is not quite correct, for I have, iu the freshly-killed biril, always 

 found a narrow, very slightly developed lobe. 



t One specimen of Cairina moschata (Lis. ), which I have examined, had no foutanelles. 

 I have seen two skulls of Olor columbianus (Ord.) which presented corresponding open- 

 ings, their limits, however, being lacerated and iu a state indicating that the ossifi- 

 cation was not yet finished. The other crania of the same siiecies show no trace of 

 these fontanelles. 



