STEGANOrODES, TOTIPALMATE BIRDS. 



297 



This is a definite and perfectly natural group, whicli will be immediately recog- 

 nized by the foregoing characters, one of which, the complete webbing of the 

 hallux, is not elsewhere observed among birds. It is represented by six genera, 

 all North American, each the tj^pe of a family. 



The nature is altricial throughout the order. The eggs are very few, frequently 

 only one, usually if not always plain-colored, and encrusted with a peculiar white 

 chalky substance ; they are deposited in a rude bulky nest on the ground, on rocky 

 ledges, or on low trees and bushes in the vicinity of water. The dietetic regimen 

 is exclusively carnivorous, the food being chiefly fish, 

 sometimes pursued under water, sometimes plunged 

 after, sometimes scooped up. In accordance with this, 

 we find the alimentary canal to consist of a capacious 

 distensible ossophagus not developing a special crop, 

 a large proventriculus with numerous solvent glands, a 

 small and very moderately muscular gizzard, rather 

 long and slender intestines, with small coeca, if any, 

 and an ample globular cloaca. The tongue is extremely 

 small, a mere knob-like rudiment (as we have seen in 

 the piscivorous kingfishers). The characteristic gular 

 pouch varies greatly in development. The condition of ^"^- ^'"- '-1'o"p''1™'''« i"™*- 

 the external nostrils is a curious and unexplained feature ; they appear to be open at 

 first, and in some species, like the tropic-bird, they remain so ; but they are gener- 

 ally completely obliterated in the adult state. There are probably no intrinsic 

 syringeal muscles in any birds of this order. But the most notable fact in connec- 

 tion with the respiratory system is the extraordinary pneumaticity- of the body, 

 which reaches its height in the pelicans and gannets ; it is described by Nitzsch 

 substantially as follows : The interior air receptacles are of an ordinary character, 

 but the anterior of these cells are more subdivided than usual ; from tliem, the air 

 gets under the skin through the axillary cavities, and diff'ases over the entire 

 pectoral and ventral regions, in two large parallel inter-communicating cells on 

 each side, over which the skin does not fit close to the bod3r, but hangs loosely. It 

 is further remarkable that the skin itself does not form a wall of these cavities, a 

 very delicate membrane being stretched from the inwardly projecting bases of the 

 contour-feathers. Thus there is yet another, although a very shallow, interval 

 between this membrane and the skin, this also containing air, admitted from the 

 larger spaces by numerous minute orifices close to the roots of the feathers. This 

 subcutaneous areolar tissue is that which, in ordinary birds and mammals, holds the 

 deposit of fat, no trace of which substance is found in these birds. 



The pterylosis of Steganopodes adheres throughout to one marked type, there 

 being little variation except in the density of the plumage, which would seem to 

 accord with temperature, the tropical forms being the more sparsely feathered. 

 Excepting one genus, the gular sac is wholly or in part bare. The contour 

 feathers appear to always lack aftershafts. The remiges are from 26 to 40 in 

 number, of which 10 are always long, strong, pointed primaries. There are 

 usually 22-24 tail feathers in the pelicans, but 12, 14 or 16 in the other genera. 

 . All have the oil gland large, with a circlet of feathers and more than one orifice ; 

 sometimes, as in the pelicans, it is protuberant, heart-shaped, and as large as 

 pigeons' eggs, with two sets of six orifices ; in the gannets it is flat and disc-like. 



The palatal structure is desmognathous ; there are no basipterygoids ; the 

 maxillo-palatines are large and spongy ; the mandibular angle is truncate ; other 



KEY TO N. A. BIRDS. 38 



