348 TOTANUS. 



distinctly barred, so that we may fairly assume that T. incanus, the adults of which have 

 the under tail-coverts very distinctly barred, is the older form — a conclusion supported by 

 the fact that the scales at the back of the tarsus of the American form are constructed on a 

 more archaic type than in the Siberian species. T. incanus and T. semipalmatus are so 

 Atlantic and different that we may recognize their subgeneric distinction by supposing that T. semi- 

 Paciflc palmatus emigrated along the Atlantic coast of America, and T. incanus along the Pacific 



OOciSts of 



America. coast of that continent. During the warm period which followed the Post-Pliocene Glacial 

 Period the latter species appears to have sent a detachment across Behring Straits to East 

 Siberia, the descendants of which have become partially differentiated, and are now known 

 as T. incanus brevipes. 



Across Bartram's Sandpiper (T. bartrami), like the Ruff in the Old World, appears to have 



AraeriJa 111 emigrated across country in the New World, and to have become almost entirely an inland 

 species. 



Pacific coast The evidence that the ancestors of the remaining eight species emigrated along the 



Pacific coast of Asia is very strong. Four of them are Nearctic and four Palgearctic; of 

 the latter, one is absent from Western Europe, and the other three are represented by such 

 close allies in the New World that it is reasonable to suppose that the American species 

 are the result of emigrations across Behring Straits during the Post-Glacial warm period. 

 These eight species are : — 



Old World. New World. 



T. terekius. 



T. hypoleucus. T. macularius. 

 T. ochropus. T. solitarius. 

 T. glareola. T. flavipes. 

 T. melanoleucus. 



The remarkable fact that T. melanoleucus almost exactly resembles in almost every 

 dimension T. glottis suggests the possibility that the former may be the American analogue 

 of the latter (though it has lost its white lower back and rump) rather than a giant form 

 of T. flavipes, which it almost exactly resembles in colour. The fact that the young in 

 first plumage of T. macularius so closely resembles the adult of its Palaearctic analogue, is 

 strong evidence that the latter is the older form. 



T. ochropus being the commonest of the four in India, was probably differentiated in 

 that country. The extraordinary abundance of T. glareola in Ceylon suggests that island 

 as the birthplace of that species. T. hypoleucus being the most abundant of the four in 

 Burma was probably isolated in that peninsula ; whilst the range of T. terekius being the 

 least westerly, the Malay Archipelago may have been the original home of that species. 



