328 CALIFORNIA ACADEMY OF SCIENCES. 



the lower parts, while orange or chestnut are also repre- 

 sented in eight species. The following correlations of 

 color may also be noted: When white appears on the 

 throat or ear coverts it is the color of the breast and 

 abdomen; when the rump is yellow the throat is yellow 

 or white; when the top of the head is chestnut or orange, 

 the throat is generally the same (one exception); when 

 the top of the head is yellow the throat is generally 

 yellow or white; when the back is streaked the sides are 

 generally streaked. 



Genus Seiurus. The Water Thrushes, etc. 



(2) Adult male like female; young with a slightly 

 less developed plumage. 



Prevailing colors, black, white, brown, olive, orange, 

 rufous. 



The resemblance of Passerella to some of the thrushes 

 has already been mentioned, but the present genus ex- 

 hibits even more perfect similarity to the thrushes, both 

 in color and markings. The orange crown of *S. auro- 

 capillus and the greenish olive color of the back in this 

 species are of course exceptions. It would seem that 

 the markings are to be explained largely by the general 

 laws of pigment deposition, the greater amount of pig- 

 ment going to the back has made it uniform in color, 

 while the breast has retained the primitive spotted 

 plumage, the markings having been defined and accent- 

 uated by sexual selection, perhaps. The superciliary 

 stripe is a conspicuous recognition mark, and may have 

 originally been discriminative in character, distinguish- 

 ing the ancestral form of S. noveboracensis from the 

 ancestral form of ^S*. aurocapillus with a white orbital 

 ring. The colors of this latter species are similar to the 

 typical colors of the family — black, yellow (orange) and 

 olive green, but the other species are all brown. 



