42 THE ZOOLOGIST. 
semi-arctic birds, the limit of their northern range corresponding 
to a considerable extent with the isothermal lines. In North- 
west Europe, where the influence of the Gulf Stream raises the 
latitude of suitable climate, Oystercatchers breed as far north as 
lat. 70°, in East Russia and West Siberia up to 66°, but in East 
Siberia and on the American Continent only up to about 60°. 
In the Southern Hemisphere the southern limit of their breeding 
range is determined by the limitation of the land. No Oyster- 
catcher is known to breed within the Tropics on the mainland, 
but there is reason to believe that they breed on some of the 
islands within the Tropics, the Bahamas, the Galapagos Islands, 
the islands on the north coast of Australia, and possibly else- 
where; otherwise Oystercatchers are only winter visitors to the 
tropics. 
The Oystercatchers constitute the genus Hematopus, which 
belongs to the family Charadriide, a group of birds which also 
includes the Sandpipers, Snipes, Plovers, Turnstones, &c. Some 
ornithologists split this family into two, Charadriidé and Scolo- 
pacide, but the Oystercatchers are witnesses against the evidence 
of such a course. It is impossible to decide in which of the two 
pseudo-families they should be placed. The American ornith- 
ologists (whose practice of splitting amounts almost to a 
monomania) cut the Gordian knot by placing the Oyster- 
catchers in a family by themselves, which they call Hemato- 
podide ! 
In the family of Charadriide the scutellations of the tarsus 
vary to a remarkable degree. In some species the tarsus is 
covered both in front and at the back with broad scutellations, 
the front row being connected with the back row by fine reticula- 
tions which cover the side of the tarsus. In other species the 
front row of scutellated plates alone is present, the back of the 
tarsus as well as the sides being covered with fine reticulations; 
whilst in a third group the fine reticulations extend all round the 
tarsus. ‘These three groups are obviously purely artificial ones, 
and are open to another serious objection. They are not separated 
from each other by a hard-and-fast line, but many genera include 
forms which are intermediate between one aud the other. Nothing 
of this kind, however, occurs in the Oystercatchers; they all 
clearly and undoubtedly belong to the third category, in which 
the whole of the tarsus is covered by a fine network of small 
