ANATID.E: SWANS, GEESE, DUCKS. 891 



additional information respecting the structure of this, the largest and most important family 

 of swimming birds, may be desirable. It is definitely characterized by many important points 

 besides those external features just stated. In palatal structure, ^MaitcZa? are desmoguathous 

 (fig. 78) ; ''the lacrymal regicm of the skull is remarkably loug [the lacrymal bone itself is 

 largo]. The basisphenoidal rostrum has oval sessile basipterygoid facets [situated very far 

 forward]. The flat and lamellar maxillo-palatines unite and form a bridge across the palate. 

 The angle of the mandible is produced and greatly recurved " (Huxleij). Interorldtal sei)tum 

 is more or less completely ossified, and orbits are better defined than in many birds, by well- 

 developed lacrymal and post-frontal processes. Premaxillary large; its 3 prongs so extensively 

 fused that only a slight nasal aperture remains. Sometimes the top of the skull shows cres- 

 centic depressions for lodgment of the supraorbital gland, the secretion of which lubricates the 

 nasal passages; but this feature is never so marked as in most piscivorous swiuimers (fig. 63). 

 Sternum long and broad, more or less transverse posteriorly, with a simple notcli or fenestra 

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

 vertebrte vary a good deal in number, owing to variability of cervicals, wliicli run up to 23 or 

 24 in some Swans (including 2 cervico-dorsals; a Goose has 18 + 2). The ribs bear uncinate 

 processes, as usual in birds (these being absent in somewhat related or chenomorphic Anhimi- 

 d(e). Pelvis ample, arched, and extensively ossified, with small foramina, showing uotiiing 

 of the straight, constricted, largely fenestrated figure prevalent among lower water-birds. Oil- 

 gland present, tufted ; carotids 2 ; ambiens, femorocaudal and its accessory, and semi- 

 tendinosus, present. Tongue large and fleshy; its main bone (glosso-hi/al ; fig. 72) highly 

 developed ; its sides show processes corresponding to the lamellae of the bill. Gullet not so 

 ample as in flesh-eating swimmers ; gizzard like that of a fowl in 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 coeca vary with the genera according to 

 food ; they are very long — 12 or 15 inches — in some 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 Ana- 

 ticlfc a long penis is developed. It is essentially a sacular production of a highly vascular part 

 of the lining membrane 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 papillae 

 at the base of this grocjve. This form of penis has a muscle by which it can be everted, pro- 

 truded and raised" (Owen). Among the most interesting structures of ^««f/VZrt? are 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 Anfteranas 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 Cranes, Ibises, Agamis, certain GtiUiinc, and 

 tliose curious Snipe, the EostrofnUn(P.) In most Ducks, furthermore, and in Mergansers, the 

 lower larynx is singularly enlarged and complicated; several lower rings c)f the trachea being 

 sr)ldered together and greatly magnified to produce a large irregularly-shaped cajisule, the so- 

 called bulla ossea or tracheal tympanum. Its use is not known beyond its obvious effect in 

 modifying the timbre or quality of the voice ; in some sense it is a sexual character, since it is 

 only fully developed in the ^ as a rule, though present in the 9 I'f Virago cctstattea ; it varies 

 greatly in size and shape in different s))ecies (figs. 3, 08), as well as in tlie relative extent to 

 which hard gristle and s<ift membrane enter into its comjinsition. Finally, it slmnld be added, 

 the pterylosis of the family is perfectly definite, a certain type of tract-formation prevailing 

 throughout, with very slight minor modifications, and always j)resentini; a ventral apteriuin. 

 It is not easy to overrate the eciinomic impnrtance of this large family. It is true that 



