CHAP. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 



29 



examples of very restricted range ; but what is perhaps more 

 interesting are those cases in which a family contains numerous 

 species and sometimes even several genera, and yet is confined 

 to a narrow area. Such are the golden moles (Chrysochloridse) 

 consisting of two genera and three species, confined to extra- 

 tropical South Africa; the hill-tits (Liotrichidce), a family of 

 eleven genera and thirty-five species almost wholly limited to 

 the Himalayas, but with a few straggling species in the Malay 

 countries ; the Pteroptochidse, large wren-like birds, consisting 

 of eight genera and nineteen species, almost entirely confined 

 to temperate South America and the Andes ; and the birds-of- 

 paradise, consisting of nineteen or twenty genera and about 

 thirty-five species, almost all inhabitants of New Guinea and 

 the immediately surrounding islands, while a few, doubtfully 

 belonging to the family, extend to East Australia. Among 

 reptiles the most striking case of restriction is that of the 

 rough-tailed burrowing snakes (Uropeltidae), the five genera 

 and eighteen species being strictly confined to Ceylon and 

 the southern parts of the Indian Peninsula. 



The Distribution of Orders. — When we pass to the larger 

 groups, termed orders, comprising several families, we find com- 

 paratively few cases of restriction and many of world-wide 

 distribution ; and the families of which they are composed arc 

 strictly comparable to the genera of which families are com- 

 posed, inasmuch as they present examples of overlapping, or 

 conterminous, or isolated areas, though the latter are com- 

 paratively rare. Among mammalia the Insectivora offer the 

 best example of an order, several of whose families inhabit 

 areas more or less isolated from the rest ; while the Marsupialia 

 have six families in Australia, and one, the opossums, far off in 

 America. 



Perhaps, more important is the limitation of some entire 

 orders to certain well-defined portions of the globe. Thus the 

 Proboscidea, comprising the single family and genus of the 

 elephants, and the Hyracoidea, that of the Hyrax or Syrian 

 coney, are confined to parts of Africa and Asia ; the Marsupials 

 to Australia and America ; and the Monotremata, the lowest of 

 all mammals — comprising the duck-billed Platypus and the 



