132 ZOOLOGICAL GEOGRAPHY. [part hi. 



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 Sealops, a genus of moles ; as well as the skunk 

 {Mephitis), American badger {Taxidea), racoon {Procyon), pouched 

 rat {Geomys), beaver rat {Fiber), jumping mouse {Jaculus), 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 Crotophaya, a South American 

 genus usually associated with the cuckoos. Helmintherus and 



