686 



MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



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renamed the same form helcheri in 1842, and BairH, in 1855, distinguished 

 Sciurus suckteyi, which two years later, after the reception of additional 

 specimens, ho himself referred to douglassL The S. lanuginosus of Bach- 

 man is based on a white-bellied, light-colored specimen, said by Townsend 

 io have been collected at Sitka. It agrees very well with the light-colored, 

 white-bellied phase of douglasxi from Fort Crook, Cal, and I have little 

 doubt is referable to douglassi. ProfesRor Baird, however, regarded it, afl;er 

 an examination of the specimen, as an albinistic example of S. richardsoni, 

 admitting, however, that it is possibly referable to douglassi, which view the 

 locality, if correctly stated, certainly favors. To this variety is also refera- 

 ble the S. moliipiloms of Audubon and Bachman, 1)ased on a specimen from 

 the "northern parts of California", in which the lower parts were cinereous, 

 slightly tinged in places with rufous. 



The form next specifically distinguished was the S. richardsoni of Bach- 

 man, based on a small specimen from the "higii range of the Rocky Mount- 

 ains, west of the great chain " (probably the Bitter Root Range). It is not 

 tiie same, however, as the S. htidsonius var. fi of Richardson, as supposed 

 by Bachman. This is the origin of the name richardsoni, which appears to 

 have no synonyms. 



Var. /rcOTon/i was first described by Audubou and Ba>'hman, in 18.^3, 

 from a specimen collected by Frdmi t in the vicinity of the South Pass. A 

 second specimen, from Sawatch Pass, Avas described by Baird in 1867, at 

 which time these two were the only specimens known. This form is olso 

 fortunately without synonyms. Gray, in 1867, regarded it as a variety of 5. 

 douglassi. 



Since 1857, when Professor Baird treated each of these forms os dis- 

 tinct species, the material available for their study hos vastly increased. The 

 specimens of var. fremonti have increased from the two then known to 

 upward of fifty. The five specimens of var. richardsoni have increased to 

 upward of forty. Many additional examples of var. douglassi have also come 

 to hand, together with a large series from Northwestern Wyoming, collected 

 under the auspices of the present Survey, illustrating the unquestionable 

 intergradation of the Rocky Mountain forms with the eastern or hudsonius 

 type. While this additional material places beyond reasonable doubt the 

 complete intergradation of these diverse geographical forms, the exact 

 boundaries of their respective habitats remain yet to be determined, as well 



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