STREPSILAS. 



409 



Strepsilas. 



GEOGRAPHICAL DISTRIBUTION 



(during the breeding-season). 



Arctic Region. 



INTERPRES 

 MELANOCEPHALUS 



Circumpolar. 

 Alaskan Coast. 



Aphriza. 



VIRGATUS. 



The genus Strepsilas must be regarded as Arctic, though one of the three species Climatic dis- 

 which it contains occasionally breeds in the Temperate Region. The distribution of these tnbutl0n - 

 birds is as follows : — 



Arctic America 2 



Arctic America and Arctic and Temperate Eurasia . . 1 



Species of Strepsilas — 3 



The fact that S. interpres is still found in Greenland, Iceland, and Spitzbergen is 

 suggestive of the isolation of its ancestors in the Atlantic. The Californian coast being 

 the winter-quarters of S. melanocephalus, is a reason for supposing that its ancestors escaped Emigra- 

 from the Polar Basin through Behring Straits, and were isolated on the American shores 

 of the North Pacific ; whilst S. virgutus, wintering on the west coast of South America, is 

 probably the descendant of the Turnstones which were isolated during the Post-Pliocene 

 Glacial Period on the American shores of the South Pacific. It has the long narrow 

 wings of S. interpres, which might be expected of a species which crossed the tropics on 

 migration. 



The Turnstones breed on the coasts in the arctic and semi-arctic regions, both in the 

 Old and New Worlds. In winter they are found on the coasts of every other part of the 

 globe. 



KEY TO THE SPECIES. 



Only three species are known, which may be diagnosed as follows : — 



Chin and centre of upper 

 throat brown or streaked . 

 with brown ; not pure 

 white. 



interpres • • • 

 melanocephalus 

 . virgatus ■ ■ 



1 



Lower back pure white. 



Bill vaulted at the tip like that 

 of a Plover. 



3g 



