chap, ii.] THE ELEMENTARY FACTS OF DISTRIBUTION. 
25 
named Urotrichus, of which one species inhabits Japan and the 
other British Columbia. The cuckoo-like honey-guides, forming 
the genus Indicator, are tolerably abundant in tropical Africa, 
but there are two outlying species, one in the Eastern Hima- 
laya mountains, the other in Borneo, both very rare, and 
quite recently an allied species has been found in the Malay 
peninsula. The beautiful blue and green thrush-tits forming 
the genus Cochoa, have two species in the Eastern Himalayas, 
while the third is confined to Java; the curious genus Eupetes, 
supposed to be allied to the dippers, has two species in Sumatra, 
and the other species two thousand miles distant in New Guinea ; 
lastly, the lovely ground-thrushes of the genus Pitta, range 
from Hindostan to Australia, while a single species, far removed 
from all its near allies, inhabits West Africa. 
Peculiarities of Generic and Fam ily Distribution . — The examples 
now given sufficiently illustrate the mode in which the several 
species of a genus are distributed. We have next to consider 
genera as the component parts of families, and families of orders, 
from the same point of view. 
All the phenomena presented by the species of a genus are 
reproduced by the genera of a family, and often in a more 
marked degree. Owing, however, to the extreme restriction of 
genera by modern naturalists, there are not many among the 
higher amimals that have a world-wide distribution. Among 
the mammalia there is no such thing as a truly cosmopolitan 
genus. This is owing to the absence of all the higher orders 
except the mice from Australia, while the genus Mus, which 
occurs there, is represented by a distinct group, Hesperomys, in 
America. If, however, we consider the Australian dingo as a 
native animal we might class the genus Canis as cosmopolite, 
but the wild dogs of South America are now formed into 
separate genera by some naturalists. Many genera, however, 
range over three or more continents, as Felis (the cat genus) 
absent only from Australia ; Ursus (the bear genus) absent from 
Australia and tropical Africa; Cervus (the deer genus) with 
nearly the same range ; and Sciurus (the squirrel genus) found 
in all the continents but Australia. Among birds Turdus, the 
thrush, and Hirundo, the swallow genus, are the only perching 
