46 THE ZOOLOGIST. 
isolation of the two colonies thus produced does not appear to 
have lasted quite long enough for the complete differentiation of 
the two forms. 
These two forms represent the Pacific New World group of 
Oystereatchers, which may be characterised as having the whole 
of the plumage black, and the legs flesh-coloured. 
5. Hematopus wnicolor.—We have attempted to trace the 
history of the American detachment of Oystercatchers, and we 
must now try and follow the fortunes of the other portion which 
retreated along the shores of the Old World. The two American 
parties found a comparatively restricted coast-line at their dis- 
posal, and both of them seem to have been glad enough to retrace 
their steps, after the glacial climate had passed away, almost to 
the entrance of the Polar Sea. The Asiatic party, on the other 
hand, found a practically unlimited extent of coast-line suitable 
to their requirements. They seem to have had room and to spare 
in Australia, South Africa, and on some of the numerous islands 
in the southern half of the Eastern Hemisphere ; consequently 
they have never had occasion to recross the line to occupy once 
more their old route of emigration on the Pacific coast of Asia. 
But although they have wandered to the other side of the world, 
the fact that the two Pacific parties travelled in company for more 
than two thousand miles further than the two Atlantic parties 
could have done has produced precisely the results which we 
anticipated. The Pacific Old World Oystercatchers scarcely 
differ from the Pacific New World Oystercatchers in anything 
beyond the colour of their legs. The Australian Black Oyster- 
catcher resembles its American cousin in having the whole of its 
plumage black; but the basal half of the bill is slightly more 
elongated, and the colour of the legs and feet are brick-red, 
instead of pale flesh-colour. It is a resident throughout the 
coasts of New Zealand, Australia, and Tasmania. 
6. Hematopus unicolor capensis. — Instead of retracing their 
steps to the Behring Sea, the surplus population of the Australian 
Black Oystercatchers appear to have emigrated westwards to 
South Africa. The African Black Oystercatcher is so closely 
allied to its Australian representative that many ornithologists 
do not discriminate between them. It may, however, be recog- 
nised by its shorter bill, the basal half of which is not exceptionally 
elongated, and by the colour of its legs and feet, which are not 
