32 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



meters as follows: Wing 232; tail 124; culmen 44.7; depth 

 of bill at base 9; tarsus 20.2; middle toe 27.8. The adult 

 females average as follows: Wing 229; tail 121; culmen 

 42.2; depth of bill at base 8.4; tarsus 19.7; middle toe 27.5. 



Four adult males and two adult females from Clipperton 

 measured in millimeters in the flesh as follows : Males — 

 Lengths 345, 355, 357, 370; extents 675, 677, 685, 700. Fe- 

 males — Lengths 353, 358; extents 672, 680. 



Table V., p. 113, gives separately measurements of birds of 

 both sexes from Cocos and Clipperton islands. 



Seven eggs collected on Clipperton Island are elliptical-ovate 

 and elongate-ovate in shape, and in color and style of mark- 

 ings resemble the eggs of the common Noddy. They measure 

 in millimeters as follows: 44.8X31.5, 47.3X32.7, 43.7X32, 

 44.6X31.5, 46X30.8, 45.2X32.5, 45.6X30.8. 



Gygis alba: White Tern 



Tower Island. 



A White Tern passed close to the vessel on September 14, 

 1906, when off Tower Island. Another was captured by Mr. 

 Beck on Oneal Rock, near Socorro, Revilla Gigedo Islands, on 

 July 27, 1905. It was the only one observed among 

 thousands of Sooty Terns and Noddies. 



On August 9, 1905, the second specimen for the expedition 

 was seen near Clipperton Island, Mexico. The following day, 

 on that island, a dozen were found, in company with Brew- 

 ster's Boobies, roosting on the crossbeams of a shed, one end of 

 which had an opening, giving the birds access. 



During the voyage from Clipperton Island to Cocos Island, 

 Costa Rica, White Terns were noted as follows: 



August 29, 1905, latitude 5° 22' North, longitude 87° 5' 

 West — two. 



August 31, 1905, latitude 4° 5' North, longitude 88° 3' 

 West — a few. 



September 2, 1905 ; forty miles south of Cocos Island — 

 two or three. 



At Cocos Island they were commonest in the forests, roost- 

 ing in the trees both inland and along the coast. They were 

 seen also among the trees on the small outlying Nuez Island. 



