68 NATURAL HISTORY OF BIRDS. 



World by several geographical variations. The American germs, JPocKlymbus, is par- 

 ticularly characterized by its high and stout bill, and by the bristly feathers of the 

 forehead. The American dab-chick, P. podiceps, is common in eastern North America. 



We have here to consider a small group of birds, consisting of perhaps not more 

 than four species, and constituting a separate superfamily which we have called HELI- 

 ORNITHOIDE^E, though by no means convinced that this is the best place that could 

 be assigned to them. They are more usually referred to the neighborhood of the rails, 

 but as this position does not satisfy us better, the view of the late Professor W. A. 

 Forbes has here been followed in placing them nearer to the grebes. 



With the latter, the fin-foots, or sun-grebes, as they have also been called, agree in 

 the form of the bill, and like them they have lobated toes, which, among other things, 

 however, differ in having the middle toe decidedly longer than the outer one. Their 

 plumage is not dense and glossy like that of the grebes, from which the fin-foots differ 

 most essentially in having not less than eighteen well-developed tail-feathers. Another 

 point characteristic of the pterylosis of these remarkable birds is that the feathers 

 are without an aftershaft. The head is small, and the neck very thin and narrow. 



The fin-foots are still a great puzzle to ornithologists, for not only is their structure 

 imperfectly known, but information concerning their habits is extremely scanty. 

 Their geographical distribution is not less perplexing ; for one genus, with one species, 

 Heliornis fulica, inhabits South America, two species of the genus Podica are peculiar 

 to Africa, while a third one is at home in eastern Asia, a distribution which offers cer- 

 tain points of analogy to that of the darters. 



The South American fin-foot inhabits rivers of the Brazilian empire and other 

 eastern states on the Neotropical continent. It is about the size of the European dab- 

 chick, of a brownish olive color above, with head and upper neck black ; it is buffy 

 Avhite underneath ; neck, throat, and a postocular stripe pure white. Very characteris- 

 tic are the broad and distinct black bands which cross the joints of the yellow feet. 

 The 'picapare,' as it is called by the inhabitants, prefers shadowy and quiet rivers, 

 even those of the deep virgin forests, feeding upon fishes, water insects, and seeds. It 

 is said to sit for hours on a branch overhanging the water and half submersed, but 



dJ CI? ^5 ' 



diving is only resorted to in danger or when wounded. Two naked young ones are 

 hatched in December. Heard from a distance, the voice is said to resemble the bark- 

 ing of a small dog. 



The following superfamily, the ALCOIDE^E, is of a very varied appearance, and is 

 in many respects of great importance, not only on account of the great number of differ- 

 ing forms of which it is composed, and the zoological interest connected with them, 

 but also because the enormous number of individuals of several species make them a 

 notable object in the economy of many a tribe of mankind inhabiting the inhospitable 

 regions surrounding the north pole. In fact, the members of this superfamily are dis- 

 tinctive of the northern circumpolar fauna, and not a single one is found on the 

 southern hemisphere, nor does a single species inhabit any part of the tropical zone. 

 As a consequence of the circumpolar distribution, all the genera and nearly all the 

 species occur in America. 



We distinguish two very well defined families, the Urinatorida) and the Alcidre. 

 Externally they differ especially by the former having four, the latter only three toes. 

 A very striking anatomical difference is the presence in the former of a very powerful 

 cnemial process of the tibia in front of the knee-pan, another being that the former 

 have an ambiens muscle whit," -. the latter lack. 



