372 GEOGKAPHICAL DISTEIBUTICXS OF AK1MALS. 



hover upon the islands and shores of the North ; the shoals 

 of fishes, the salmon, among others, which throng the coasts 

 of Greenland, Iceland, and Hudson's Bay. There is uni- 

 formity also in the form and colour of these animals. Not a 

 single bird of brilliant plumage is found, and few fishes with 

 varied hues. Their forms are regular, and their tints as dusky 

 as the northern heavens. The most conspicuous animals are 

 the white bear, the moose, the reindeer, the musk-ox, the 

 white fox, the polar hare, the lemming, and various seals ; but 

 the most important are the whales, which, it is to be remarked, 

 rank lowest of all the mammals. Among the birds, may be 

 enumerated some sea-eagles and a few waders, while the 

 great majority are aquatic species, such as gulls, cormorants, 

 divers, petrels, ducks, geese, gannets, &c., all belonging to the 

 lowest orders of birds. Reptiles are altogether wanting. The 

 articulata are represented by numerous marine worms, and 

 by minute crustaceans of the orders isopoda and amphipoda. 

 Insects are rare, and of inferior types. Of the mollusca, 

 there are acephala, particularly tunicata, fewer gasteropods, 

 and very few cephalopods. Among the radiata are a great 

 number of jelly-fishes, particularly the Beroe; and to conclude 

 with the echinoderms, there are several star-fishes and echini, 

 but few holothurise. The class of polypi is very scantily repre- 

 sented, and those producing stony corals are entirely wanting. 



603. This assemblage of animals is evidently inferior to 

 that of other faunas, especially to those of the tropics. Not 

 that there is a deficiency of animal life ; for if the species are 

 less numerous, there is a compensation in the multitude of 

 individuals, and also in this other very significant fact, that 

 the largest of all animals, the whale's, belong to this fauna. 



604. It has already been said ( 602) that the arctic fauna 

 of the three continents is the same ; its southern limit, how- 

 ever, is not a regular line. It does not correspond precisely 

 with the polar circle, but rather to the isothermal zero, that is, 

 the line where the average temperature of the year is at 32. 

 of Fahrenheit. The course of this line presents numerous 

 undulations. In general, it may be said to coincide with the 

 northern limit of trees, so that it terminates where forest 

 vegetation succeeds the vast arid plains, the barrens of North 

 America, or the tundras of the Samoyedes. The uniformity 

 of these plains involves a corresponding uniformity of plants 

 and animals. On the .North American continent it extends 



