chap, li.] 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 (Chrysochloridae) 
consisting of two genera and three species, confined to extra- 
tropical South Africa ; the hill-tits (Liotrichidse), 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 j the PteroptochidEe, 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 are 
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 
