5o8 



SNODGRASS AND HELLER 



Immature Male. — Similar to adult, somewhat lighter on belly ; 

 feathers of back, wing coverts, rump and upper tail coverts with red- 

 dish-brown edgings. Lores blackish-brown. Pale color of top of 

 head dead white, lacking the pearly or plumbeous hue of the adult, 

 closely mottled or streaked with brown, ending abruptly against the 

 color of the back. No plumbeous on the sides of head or throat. 



According to Anthony this species is " much darker and less brown 

 than A. rousseatii, resembling in this respect A. g-alapagoensis^ from 

 which it differs in the much paler cap." 



We have four adult females and three immature males from Cocos 

 Island, taken in July, and three adult females from Clipperton Island, 

 taken in November. 



In the following table we give the measurements in millimeters of 

 our adult specimens from Clipperton and Cocos Islands, and also, for 

 comparison, Ridgway's averages for Anous stolidus rousseaui} 



MEASUREMENTS, IN MILLIMETERS, OF AllOllS StoUduS 



ridgwayi. 



Atious stolidus rousseaui. 



Averages. — 



Averages. I — 



278 160 



273 152 



Pacific Ocean. 

 Indian Ocean. 



This tern was very abundant in November on the high rock of the 

 eastern side of Clipperton Island, while the other one, Sterna fuligi- 

 nosa.^ kept almost exclusively in the neighborhood of the small islands 

 in the lagoon. The Anous, while sitting on the rock ledges, gave forth 

 almost incessantly a harsh chattering sound describable as a loud, 

 harsh, broken note, or better, perhaps, as several similar harsh notes 

 run together into a single series. This sound is varied by distinctly 



^Proc. U. S. Nat. Museum, vol. xix, p. 645, 1S96. 



