TOWNSEND AND ALLEN: LABRADOR BIRDS. 421 



winter migrants can for a moment be in doubt that these routes really 

 represent the way by which the species originally invaded America. 

 It would be difficult to find a more beautiful example to illustrate 

 that now well-known law which was first formulated by Prof. Johan 

 Axel Palmen, of Helsingfors. Moreover, no better example could be 

 found for demonstrating the necessity of minute discrimination in 

 ascertaining the characters by which these 'migration route races,' 

 as Palmen calls them, are characterized. 



"It seems that one more lesson can fairly be drawn from the differ- 

 entiation of the Greenland race, viz, that the Greenland-Iceland- 

 England route must be considerably older than the Alaska-Tchuktchi- 

 Udski route, since it has resulted in the establishment of a separable 

 race. A consideration of the further fact that no regular migration 

 route could have been effected between Greenland, Iceland, and 

 Great Britain during the present distribution of land and water in 

 that part of the world also leads us back to a period when the stretches 

 of ocean now separating those islands were more or less bridged over 

 by land. For such a condition of affairs we shall have to look toward 

 the beginning of the glacial period. At that time it must, therefore, 

 be assumed that the Wheatear extended its range into Greenland. 

 The advent of the typical form into Alaska, on the other hand, is 

 probably one of very recent time, an assumption corroborated by the 

 somewhat uncertain and erratic distribution of the species in that 

 northwestern corner of our continent." 



Summary. 



Authenticated species and subspecies . . . 213 



Extinct species 2 



Doubtful and erroneous species .... 44 



Total, 259 



The following table presents in the form of a summary, the approxi- 

 mate numbers of the different species of birds observed by us during 

 our journey along the coast, and is of interest as showing what species 

 are most likely to be met with on these shores, and at what points we 

 found them in greater or less abundance. 



