680 SYSTEMATIC SYNOPSIS.— LAMELLIBOSTBES—ANSEBES. 



unite and form a bridge across the palate. The angle of the mandible is produced and greatly- 

 recurved " {Huxley). The interorbital septum is more or less completely ossified, and the 

 orbits are better defined than in many birds, by well-developed lacrymal and post-frontal pro- 

 cesses. The premaxillary is large, and its three prongs are so extensively fused that only a 

 slight nasal aperture remains. Sometimes the top of the skull shows crescentio depressions for 

 lodgment of the supraoi'bital gland, the secretion of which lubricates the nasal passages ; but 

 this feature is never so marked as in most of the piscivorous swimmers (fig. 63). The sternum is 

 long and broad, more or less transverse posteriorly, with a simple notch or fenestra on each 

 side ; sometimes its keel is curiously hollowed out for a purpose stated beyond. The vertebrae 

 vary a good deal in number, owing to the variability of the cervicals, which run up to 24 in 

 some swans. The pelvis is ample, arched and extensively ossified, with small foramina, showing 

 nothing of the straight, constricted, largely fenestrated figure prevalent among lower water- 

 birds. The oil-gland is present, tufted. The carotids are two. The ambiens, femoro-caudal 

 and its accessory and semitendinosus are present. The tongue is large and fleshy ; its main 

 bone (jglosso-hyal ; fig. 72) is highly developed ; its sides show processes coiTesponding to 

 the lamellae of the bill. The gullet is not so ample as in the flesh-eating swimmers. The 

 gizzard resembles that of a fowl in its shape and great muscularity; the muscles are deep- 

 colored, and well show the typical disposition of large hemispherical lateral masses converging 

 to central tendons. The ooeca vary with the genera according to food ; they are very long — 

 12 or 15 inches — in some of the herbivorous species. The male genital armature merits 

 special notice. " In some Natatores which copulate on the water there is provision for more 

 efficient coitus than by simple contact of everted cloacae ; and in the AnatidcB a long penis is 

 developed. It is essentially a sacular production of a highly vascular part of the lining mem- 

 brane of the cloaca. ... In the passive state it is coiled up like a screw by the elasticity of 

 associated ligamentous structure. ... A groove commencing widely at the base follows the 

 spiral turns of the sac to its termination ; the sperm ducts open upon papilla? at the base of this 

 groove. This form of penis has a muscle by which it can be everted, protruded and raised." 

 (Owen.) Among the most interesting structures of the AnaUdm are the curious modifications 

 of the windpipe, prevailing almost throughout the family. In a number of swans, this organ 

 enters a cavity in the keel of the sternum, doubles on itself and then emerges to pass to the 

 lungs, forming either a horizontal or a vertical coil. In some geese the windpipe coils between 

 the pectoral muscles and the skin. These vagaries of the windpipe are not, however, confined 

 to the present family, occurring in some of the cranes, ibises, certain Gallinee, and also, it is 

 said, in the curious snipe, Bhynchesa cwpensis. In most of the ducks, furthermore, and in the 

 mergansers, the lower larynx is a singularly enlarged and complicated afiair; several of the 

 lower rings of the trachea being soldered together and greatly magnified to produce a large 

 irregularly shaped capsule. Its use is not known; in some sense it is a sexual character, 

 since it is only fully developed in the male; it varies greatly in size and shape in different 

 species (figs. 3, 98). Finally, it should be added, that the pterylosis of the family is perfectly 

 definite, a certain type of tract-formation prevailing throughout, vrith very slight minor modi- 

 fications. 



It is not easy to overrate the economic importance of this large family. It is true that the 

 mergansers, some of the sea ducks, and certain maritime geese, that feed chiefly upon animal 

 substances, are scarcely fit for food ; but the great majority afford a bounteous* supply of sapid 

 meat, a chief dependence, indeed, with the population of some inhospitable regions. Such is 

 the case, for example, in the boreal parts of this continent, whither vast bands of water-fowl 

 resort to breed during the fleeting arctic summer. Their coming marks a season of compara- 

 tive plenty in places where hunger often pinches the beUy, and their warm downy covering 

 k patched into garments almost cold-proof. 



The general traits of the anserine birds are too well known to require more than passing 



