654 SYSTEMATIC SYNOPSIS ^HERODIONES—HEROBII. 
14. Suborder HERODII : The Heron Series. 
Skull holorhinal. Angle of mandible truncate. Ambiens muscle, and accessory femoro- 
caudal, absent ; femoro-caudal, semitendinous and its accessory, present. Carotids double, 
sometimes abnormal (p. 198). One intestinal coecum. Tongue moderate. A tufted oil-gland. 
Plumage with 2-4 pairs of powder-down tracts ; feathered tracts very narrow. Tarsi normally 
scutellate. Hallux long and perfectly insistent, with long claw. Inner edge of middle claw 
distinctly pectinate. Bill variable with the families, normally narrow and wedged, with long 
nasal fossae. 
The extraordinary Balceniceps rex, the Shoe-bill or Whale-head, of Africa, with an 
enorn^ous head and bill, thick neck, and one pair of powder-down tracts, is the type of a family 
• Bal(Bnicipitid(Bj which may belong here ; but it approaches the Storks, and its peculiarities are 
so great that it may constitute a separate superfamily group. The Boat-billed Heron (Cancroma 
cochlearici) of Central America, with a singular shape of bill that has suggested the name, and 
four pairs of powder-down tracts, constitutes one femily of Herodii (Cancromidcc). The dis- 
puted cases of Euryprjga and Scopus have already been mentioned. These and some other 
doubtful forms aside, the Heron series is represented by the single 
46. Family ARDEID^ : Herons. 
It is in this family, as in CancromidcB, that powder- down tracts reach their highest devel- 
opment ; and although these peculiar feathers occur in some other birds, there appears to be 
then only a single pair so that the presence of two or three pairs is probably diagnostic of 
this family. In the genus Ardea and its immediate allies (Ardeince) there are three pairs, 
the normal number; one on the lower back over the hips, one on the lower belly under the 
hips, and one on the breast, along the track of the furcula. In the Bitterns (Botaurince) the 
second of these is wanting. (In the Boat-billed Heron, Cancroma cochlearia, there is still 
another pair, over the shoulder-blades.) There are other pterylographic characters ; in gen- 
eral, the tracks are extremely narrow, often only two feathers wide ; there are lateral neck 
tracks ; the lower neck is frequently bare behind. More obvious characters are, the complete 
featliering of the head (as compared with Storks, etc.) except definite nakedness of the lores 
alone — the bill appearing to run directly into the eyes ; a general looseness of the plumage 
(as compared with Limicolce), and especially the frequent development of remarkably length- 
ened, or otherwise modified, feathers, constituting the beautiful crests and dorsal plumes that 
ornament many species, but which, as a rule, are worn only during the breeding season. 
These features will suffice to determine the Ardeidce, taken in connection with the more general 
ones indicated under head of Herodiones, and the following details : — 
Bill longer than head, usually about as long as tarsus, straight, or very nearly so, more 
or less compressed, acute, cultrate (with sharp cutting edges) ; upper mandible with a long 
groove. Nostrils more or less linear, pervious. Head narrow and elongate, sloping down to 
the bill, its sides flattened. Lores naked ; rest of head feathered, the frontal feathers extending 
in a rounded outline on the base of the culmen, generally to the nostrils. Wings broad and 
ample ; the inner quills usually as long as the primaries, folding over them when the wing is 
closed. Tail very short; of twelve (usually) or ten (in Zebrilus and Botaurince) soft broad 
feathers. Tibiae naked below (except Zebrillus), sometimes for a great distance. Tarsi 
scutellate in front (except Tigrisoma), and sometimes behind, generally reticulate there and 
on the sides. Toes long and slender ; the outer usually connected with the middle by a basal 
web, the hinder very long (for wading birds), inserted on the level of the rest. Hind claw 
larger and more curved than the middle one (always ?) ; the middle claw pectinate. 
The group thus defined offers little variation in form ; all the numerous genera now • 
