158 Umvcrsity of California Publications in Zoology. [Vol. 7 



by P. m. hylacus are very small, and still farther west we come 

 abruptly to an exceedingly large form, M. coronarius. This does 

 not appear to intergrade with 31. macrurus, just as P. sitkensis 

 does not with P. m. hylaeus, but nevertheless in each case 

 they seem to be merely gigantic insular races. 



The mammals of general distribution are surprisingly few 

 in number. The otter (Lutra) ranges, apparently unchanged, 

 throughout the region, and it is easy to see why it should. Beaver 

 occur on most of the larger islands, but according to Heller 

 (1909, p. 251) those from the more southern islands are a 

 different form from the northern ones. Deer also are found 

 throughout the archipelago ; but I am strongly of the impression 

 that the deer found south of Frederick Sound will prove to be 

 distinct from the more northern 0. c. sitkensis. A species of 

 shrew {Sorex ohscurus) is found apparently on every island and 

 all along the mainland coast, and there is surprisingly little 

 variation in the series from different points. Those from the 

 northern islands, however, appear to be referable to *S^. o. glacial is, 

 from the southern to S. o. longicaiula. 



The land birds of the Sitkan district are for the most part 

 the same as, or closely related to, species ranging along the main- 

 land coast farther south. The equable and comparatively warm 

 climate of this region, compared with the interior at the same 

 latitude, is apparently responsible for this, permitting along the 

 coast the northern extension of the ranges of species whose centers 

 of distribution lie much farther south. Such species as Cyanocitta 

 stelleri, Colaptes cafer saturatior, Sphyrapicus varius ruber, 

 and Empidonax difflcilis, some of the commonest and most char- 

 acteristic birds of the Sitkan district, are examples of birds 

 whose ranges extend much farther north along the coast than in 

 the interior. Many species find their northern limit in this 

 region, while a few extend somewhat farther north and west 

 along the Alaskan coast. Almost none of the birds of this region, 

 however, are also found in the cold, dry interior. The exceptions 

 are mostly species of northern derivation, occurring here in the 

 Alpine- Arctic Zone of the mountain tops, the ptarmigan (which 

 has undergone some change, however) and the titlark being good 

 examples of this class. 



