1916] 



Taylor: Beavers of Western Nortli America 



447 



XVII. EXTERNAL MEASUREMENTS* OF Castor subauratus subauratus, 

 FROM STANISLAUS COUNTY, CALIFORNIA 



Specimens arranged approximately in order of age from the top of table to 

 bottom 



(All measurements in millimeters) 



*For method of taking measurements see Taylor, 1911,' p. 207. 



fFrom crown of head to tip of ear, measured on medial surface of pinna. 



JEntrails removed. 



pacificus is thicker than that in the series of subauratus, concealing 

 the darker underfur more effectually. 



Illustrative of modification in coloration within the same sub- 

 species are the following observations on the coloration of base of 

 tail. One specimen of Castor s. subauratus (no. 16383) has the 

 coloration dorsally in this region paler than the rest of the series, 

 approximately clay color. Ventrally the hairs are chestnut for 

 nearly all their length. In another example (no. 8869) the hairs 

 are pale in coloration both above and below, the colored ends being 

 hazel instead of chestnut. In no. 12654, the type of subauratus, 

 the hairs of this region are darker than the average of the rest of 

 the series. Variation of about this amount is noted in all the sub- 

 species of which adequate series are available. With all this modi- 

 fication, however, the series of ten skins of subauratus is remark- 

 ably uniform in general coloration. 



The general aspect of the subauratus series is darker than that 

 in froudator, the difference being due to darker underfur. 



