788 SYSTEMATIC SYNOPSIS. — PYGOPODES. 



as by the feet. Few other birds, such as cormorants and anhingas, resemble the Pygopodes 

 in this respect. The legs are so completely posterior, that in standing the horizontal position 

 of the axis of the body is impossible ; the birds rest upright or nearly so, the whole tarsus 

 being often applied to the ground, while the tail affords additional support ; progression 

 on laud is awlvward and constrained, only accomplished, in most cases, with a shuffling 

 moti(.in, when the belly partly trails on the ground. One species of auk could not fly at all, 

 because the wings, although perfectly formed, were too small to support the body. The rest 

 of the order fly swiftly and vigorously, with continuous wing-beats. The rostrum varies 

 in shape with the genera ; but it is never extensively membranous, nc^r lamellate, nor 

 furnished with a pouch. The nostrils vary, but are neither tubular nor abortive. The 

 wings are short, never reaching when folded to the end of the taU. The tail is short, never 

 of peculiar shape, generally of many feathers ; there are, however, no perfect rectrices in 

 the grebes. The crura are almost completely buried, and feathered nearly or quite to the 

 heel. The tarsus is usually compressed, sometimes, as in the loons, extremely so. The front 

 toes are completely palmate in the loons ;ind auks ; lobate, with basal webbing, in the grebes ; 

 the hallux is present and well formed, with a membranous expansion, in loons and grebes, 

 wanting in the auks. The plumage is thick and completely waterproof: once observing 

 some loons under peculiarly favorable circumstances in the limpiil water of the Pacific, I saw 

 that bubbles of air clung to the plumage whilst the birds were under water, giving them a 

 beautiful spangled appearance. The pterylosis shows both cont(jur and down-feathers, both 

 after-shafted; there are definite apteria; the auks have free outer branches of the inferior 

 tract-l)anils, wanting in the loons and grebes. The cjil-gland is large with several orifices. 

 Among osteological characters should be particularly mentioned the long apophysis (_)f the 

 tibia found in the loons and grebes, but not in the auks. In auks, the elbow has two 

 sesamoids. The thoracic walls are very extensive; the long jointed ribs grow all along 

 the backbone from the neck to the pelvis, and form with the long broad sternum a bony 

 box enclosing much of the abdominal viscera as well as those of the chest, perhaps to prevent 

 their undue compression under water. The top of the skull has a pair of crescentic depres- 

 sions for lodgment of a largo gland ; the palate is schizognathous. The sternum has a 

 different shape in each of the families. There are two carotids, except among the grebes, 

 and in Alle. The digestive system shows minor modifications, but accords in general with 

 the piscivorous regimen of the whole order. The sexes are alike; the young different; the 

 seas(.)nal changes often great. The auks are altricial, the loons and grebes praecocial. 

 There are three families of Pygopodes, sharply distinguished by external characters ; all of 

 them are fully represented in this country, where all the known species of loons and auks 

 occur. The penguins {Spheniseomorphm) , formerly included in this order, are better left to 

 stand by themselves ; they are confined to the Southern Hemisphere, where they are represented 

 by several genera (as Aptenodytes, Pygoscelis, Eudypites and Spheniscus) and about 13 species. 

 The wings are reduced to mere flippers, without true remiges, unfit for flight, but very efficient 

 as fins in swimming under water. Much of the plumage is harsh and scaly. There are numerous 

 osteological characters, among them the flatness and solidity of the wing-bones, and the incom- 

 plete fusion of the metatarsals. The elbow has a pair of sesamoids, and the knee a large 

 irregularly shaped patella. The feet are four-toed, and palmate. 



Analysis of Families. 



Lnnns. Feet 4-toed, palmate C0LYMBID.B 



Grelji;s. Feet 4-toed, lobate PomciPEDID.E 



Auks. Feet3-toed, palmate ALCii).ffi! 



