132 
ZOOLOGICAL GEOGRAPHY. 
[part III. 
may be to some extent due ; but there can be little doubt that it 
is also positively, and not merely relatively, more productive in 
varied forms of animal life than either of the other sub-regions. 
Mammalia . — There seems to be only one genus absolutely 
peculiar to this sub-region — the very remarkable Condylura, or 
star-nosed mole, only found from Pennsylvania to Nova Scotia, 
and as far as about 94° west longitude. It also has opossums 
(Didelphys) in common with California, and three out of four 
species of Scalops, a genus of moles ; as well as the skunk 
(Mephitis), American badger ( Taxidea ), racoon (Procyon), pouched 
rat ( Geomys ), beaver rat (Fiber), jumping mouse (Jamlus), tree 
porcupine (Erethizon), and other characteristic Nearctic forms. 
Birds . — The birds of this sub-region have been carefully 
studied by American naturalists, and many interesting facts 
ascertained as to their distribution and migrations. About 120 
species of birds are peculiar to the east coast of the United 
States, but only about 30 of these are residents all the year 
round in any part of it ; the bird population being essentially 
a migratory one, coming from the north in winter and the south 
in summer. The largest number of species seems to be congre- 
gated in the district of the Alleghany mountains. A consider- 
able proportion of the passerine birds winter in Central America 
and the West Indian Islands, and go to the Middle States or 
Canada to breed ; so that even the luxuriant Southern States do 
not possess many birds which may be called permanent resi- 
dents. Thus, in East Pennsylvania there are only 52, and in 
the district of Columbia 54 species, found all the year round, 
out of about 130 which breed in these localities ; very 
much below the number which permanently reside in Great 
Britain. 
This sub-region is well characterised by its almost exclusive 
possession of Ectopistes, the celebrated passenger pigeon, whose 
enormous flocks and breeding places have been so often de- 
scribed; and Cupidonia , a remarkable genus of grouse. The 
only Nearctic parrot, Conurus carolinensis , is found in the 
Southern States ; as well as Crotophaga, a South American 
genus usually associated with the cuckoos. Helminiherus and 
