262 CALIFORNIA ACADEMY OF SCIENCES. 



colors of the young would seem to indicate that the 

 ancestral form was much more diversified in its mark- 

 ings. The plumage of the young is much spotted with 

 black and white on a ground of light brown, and with 

 a medium stripe of black on the head and patches of 

 dusky on the ear coverts. Three species, formed by 

 geographical isolation. 



Genus PsDiociETES. Sharp-tailed Grouse. 



(3) Male like female; young like some ancestral stage 

 of the adult. 



Prevailing colors, black, white, brown, gray. 



Colors protective, the round white spots on the wings 

 for recognition. The sexual characters are in a very 

 undeveloped state, there being no very obvious differ- 

 ence in the colors of the sexes. The young are much 

 spotted, but also barred with black and streaked with 

 white. 



Genus Centrocercus. Sage Grouse. 



(7) Male dift'ering slightly from female, young like 

 female but with markings less sharply defined. 



Prevailing colors, black, white, gray, buffy, brown. 



It is difficult to say whether the colors of this bird 

 are of any great utilitarian significance or not. The 

 only recognition mark is an imperfectly defined white 

 crescent on the throat surrounding a patch of black* 

 which is replaced by white in the female. The general 

 colors may be protective, but are not peculiarly so, and 

 this may be another bird which is on the road to the 

 assumption of a melanistic plumage. The young lack 

 the spotted plumage characteristic of so many of the 

 family. 



