GAVIIDM: LOONS, OR DIVERS. 1047 



in Loons and Auks ; lobate, with basal webbing, in Grebes ; hallux present and well formed, 

 with a membranous expansion, in Loons and Grebes, but wanting in Auks. The plumage is 

 thick and completely waterproof; once observing some Loons under peculiarly favorable cir- 

 cumstances in the limpid 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 ptery- 

 losis shows contour- and down-feathers, both aftershafted ; there are definite apteria ; Auks 

 have free outer branches of the inferior pterylse, wanting in Loons and Grebes. The oil-gland 

 is large, with several orifices. Among osteological characters should be particularly mentioned 

 the long apophysis of the tibia in Loons and Grebes, but not in Auks. The thoracic walls 

 are very extensive ; long jointed ribs grow all along the backbone from neck to pelvis, and 

 form with the long broad sternum a bony box enclosing umch of the abdominal viscera as 

 well as those of the thorax, perhaps to prevent their undue compression under water. In 

 Auks and Loons, the top of the skull has a pair of crescentic depressions for lodgment of 

 large glands; the palate is schizognathous, and the nasals are schizorhinal in Auks, but ho- 

 lorhinal in Loons and Grebes. Basipterygoids are lacking or rudimentary ; lacrymals small, 

 not reaching zygoma ; the vomer is cleft behind, and maxillopalatines laminate. The sternum 

 has a different shape in each of the families. There are two carotids, except among Grebes, 

 and in the genus Alle. The digestive system shows minor modifications, but accords 

 in general with the piscivorous regimen of the whole order. Sexes are alike; young mostly 

 difi'erent; seasonal changes often great. Auks are altricial or nidicolous ; Loons and Grebes 

 praecocial or nidifugous. There are three families of Pi/gopodes, sharply distinguished by ex- 

 ternal characters ; all of them are fully represented in this country, where all the known species 

 of Loons and Auks occur. (The Penguins, Impennes, Sqiiamipennes, Ptilopteri, or Sphenisco- 

 morphce, formerly included in this order, are better left to stand by themselves. They are 

 confined to the Southern Hemisphere, where they are represented by 6 genera, Aptenodytes, 

 Pi/goscelis, Catarrhactes, Megadnptes, Eudijptula, and Spheniscus, and about 17 species of one 

 family, SpheniscidcB. The wings are reduced to mere flippers, with very numerous undeveloped 

 remigcs, unfit for flight, but very eflficieut as fins in swimming under water; there are no 

 apteria ; much of the plumage is harsh and scaly. There are numerous strong osteological 

 characters, among them flatness and solidity of wing-bones, and incomplete fusion of metatar- 

 sals. The elbow has a pair of sesamoids, and the knee a large irregularly -shaped patella. 

 The feet are 4-toed and palmate.) 



Analysis of Suborders and Families. 



Loons. Feet 4-toed, palmate Gavi-e or Gaviid^ 



Grebes. Feet 4-toed, lobate .... Podicipedes or Podicipedid.*; 



Auks. Feet 3-toed, palmate Alce or ALCiDiK 



SuBORDKR GAVI^ : Loons. 

 The characters of the subordc^r are the same as those of its single family, as follows: — 



Family GAVIID.^ : Loons, or Divers. 



(CoLYMBiD^ of Key, 187::>-90. Ukinatoriu.e of A. 0. U. 1880-0.").) 



Hill stont, straight, compressed, tapering, acute, paragnathous, entirely horny. Nostrils 

 narrowly linear, their upper edge lobed. Head completely feathered; anti.e prominent, acute, 

 reaching nostrils; no crests nor rufl's. Wings .'strong, with ID stitt" developed primaries (11 in 

 all) and many short secondaries ; aquintocubital. Legs completely posterior, buried, feathered 

 to the heel ; tarsi entirely reticulate, extremely compressed, the back edge smooth ; toes 4, the 

 anterior palmate, the posterior semilateral, not elevated, and having a lobe connecting it with 



