208 CALIFORNIA ACADEMY OF SCIENCES. 



ANTROSTOMUS. 



,. . 1 o terminal third of three outer tail-feathers white or buflfv. 



caroltnensis J •' 



{ 



? no white or buffy on tail. 

 / S four outer tail-feathers with 



CHhcuu'iixi.i ... ) '' '^ 'P' I White patch occupy 



? three outer tail-feathers with j' .^^^ ^^^^ ^^^^ ^^^^._ 



^ buff tip. V ^^j ^^.^.^^ ^^j ^^. 



1i three outer tail-feathers with ( creasina in extent 



white tip. \ from exterior feather 



$ three outer tail-feathers with 

 buflf tip. 



■^ S White piitch, occu- 



I PJ'i'^D nrore than ter- 

 vociferii.i — Tail patch more extended. ■ , ,,. , , . 



■■ I minal third, and in- 



I creasing i n extent 



vociferits arr.omi- — Tail patch less extended. * „ j. • * ii 



■' '^ from exterior feather 



? No white tail patch 



There are many interesting questions opened by this 

 survey of the tail markings of the Caprimulgidte. Tlie 

 initial markiirgs were doubtless discriminative in nature 

 coupled in many instances with other marks such as 

 the wing bars and throat patch, and were of use at the 

 time when each of the present four genera was a species 

 diverging from a common stock. As the species became 

 more and more distinct, and in some instances more 

 completely isolated geographically, these marks were no 

 longer of necessity for purposes of discrimination and 

 gradually became of service as directive marks. Then, 

 as the species of Antrostomus began to divide up into a 

 number of forms, a new set of discriminative marks be- 

 came necessary. The white patch occupying less than 

 the terminal third and decreasing in extent from the 

 exterior feather would present a very different general 

 effect from the patch occupying more than the terminal 

 third and increasing in extfent from the exterior. If 

 these markings be discriminative in their nature it is 

 possible to understand why they would be more constant 

 and more completely developed in the male than in the 



