EXTERNAL PARTS OF BIRDS.— THE FEET. 131 
exhibit the transition from the perching to the gradient foot, in some reduction of the hind toe, 
which is nevertheless in most cases still on the same level as the rest (fig. 38, 6). In the 
gallinaceous or rasorial (Lat. rasor, a scraper) birds, which are essentially terrestrial, and 
noted for their habit of scratching the ground for food, the hind toe is decidedly elevated and 
shortened in almost all of the families (fig. 35). Such reduction and uplifting of the pone is 
carried to an extreme in most of the waders, or gral- 
latores, in many of which this toe disappears (figs. 
38, a, 39). Itis scarcely practicable to recognize special 
modifications of such gradient or grallatorial feet, since 
they merge insensibly into one another. The herons, 
whieh are the most arboricole of the waders, exhibit a 
reversion to the insessorial type, in the length and in- 
cumbency of the hallux. The mode of union of the 
Fic. 48, — Semipal- 
mation in Ereunetes; front toes of the walkers and waders is somewhat char- een Ba ae? 
‘ oye . . paimate: 0! 
nat. size. acteristic. The toes are either cleft quite to the base, toes of Symphemia; 
or there jomed by small webs; probably never actually coherent. Such nat. size. 
basal webbing of the toes is called semipalmation (‘‘half-webbing”). It is actually the 
same thing that occurs in many birds of prey, in most gallinaceous birds, etc. ; the term is 
mostly restricted, in descriptive ornithology, to those wading birds, or grallatores, in which it 
occurs. Such basal webs generally run out to the end of the first, or along part of the second, 
phalanx of the toes; usually farther between the outer and middle 
than between the middle and inner toes. Such a foot is well illus- 
trated by the semipalmated plover (AZgialites semipalmatus), 
semipalmated sandpiper (Ereunetes pusillus, fig. 48), and willet 
(Symphemia semipalmata, fig. 49). In a few wading birds, as the 
avocet and flamingo, .the webs extend to the ends of the toes. 
This introduces us at once to the third main modification of the 
foot, 3. The natatorial type. Here the foot is transformed into 
a swimming implement, usually with much if not entire abrogation 
of its function as foot or hand. Swimming birds with few ex- 
ceptions are notoriously bad walkers, and few of them are perchers. 
The swimming type is presented under two principal modifica- 
tions : — (a.) In the palmate or ordinary webbed foot, all the front Fie. 50. — Palmate foot of a 
toes are united by ample webs (fig. 50). The palmation is usually tern, Sterna forstert ; nat. size. 
complete, extending to the ends of the toes; but one or both webs may be so deeply incised, 
that is, cut away, that the palmation is practically reduced to semipalmation, as in terns of 
the genus Hydrochelidon (fig. 51). The totipalmate is a special case of palmation, in 
which all four toes are webbed; this characterizes the whole order 
Steganopodes (fig. 52). (0.) In the lobate foot, a paddle results not 
from connecting webs, but from a series of lobes or flaps along the 
sides of the individual toes; as in the coots, grebes, phalaropes, and 
sun-birds (Heliornithide). Lobation is usually associated with semi- 
palmation, as is well seen in the grebes (Podicipedide). In the snipe- 
like phalaropes (Phalaropodide), lobation is present as a modification 
of a foot otherwise quite cursorial. The most emphatic cases of loba- 
tion are those in which each joint of the toes has its own flap, with a 
Fig. 51. — Incised pal- 
free convex border; the membranes as a whole therefore present a scol- mation of Hydrochelidon 
loped outline (figs..53, 53 bis). Such lobes are merely a development '@”/rmés; nat. size. 
of certain marginal fringes or processes exhibited by many non-ldbate or non-palmate birds. 
Thus, if the foot of some of the gallinules be examined in a fresh state, the toes will be seen to 
