94 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH Ser. 
MEASUREMENTS (in millimeters) 
Upper Mandible Middle 
No. | Sex | Length | Extent | Wing| Tail |Culmen| _|, _..__ | Tarsus |Toe and 
Depth | Width Claw 
1111 234 97 | 25 7.9 | 10 De 39.1 
1113 230 95 | 27 8.5 | 11.6 | 27.4 | 37.5 
1115 231 93 | 24.3 8 11.4 | 27 36.8 
AOD CO ele SD Oran es Pie Nac ayes see 96 | 25.9 8.4 | 11.5 | 28.6 | 33.9 
1110 231 94} 25.1 8.1 | 11 27.3 | 35.2 
1112 225 97 | 24.5 8.1 | 11 27.7 | 38.5 
1114 227 94 | 26.2 9 12 28 39.1 
1116 231 96 | 26 8.5 | 11.6 | 28 38 
Pterodroma cooki (Gray): CooKk’s PETREL 
SaLvin—CEstrelata cooki, 399, 417; CEstrelata defilippiana, 399, 417. 
GopmMaN—CEstrelata cooki, xlv, 247, pl. 71; Cstrelata deflippiana, 
xlv, 245, pl. 70. 
Cook’s Petrels were common during the afternoon of July 
22, 1905, in latitude 22° 257 N., longitude 1127 407 W. The 
Academy was becalmed at the time and they were attracted to 
its vicinity by a school of small fish. Mr. R. H. Beck shot 
nineteen, of which eleven were skinned and five preserved in 
alcohol. During the next two days there was a strong north- 
easterly wind and a single individual only was noted. On the 
25th another was seen, the last one for the entire voyage. 
This petrel is apparently a Southern Hemisphere species that 
has an exodus-migration that extends north of the Equator. 
Aestrelata defilippiana Giglioli & Salvadori appears to be 
merely a synonym, for no constant differences are found that 
separate Eastern from Western Pacific birds. In most of the 
Expedition specimens the dark marking at the eyes is more 
prominent than in two New Zealand ones (No. 24341 Carnegie 
Mus.; No. 109193 U. S. Nat. Mus.). Dr. (Godman’s state= 
ment that the general color is paler and the bill shorter and 
stouter’ in Eastern Pacific examples is not sustained in the 
material before me. As these petrels darken with wear, much 
stress should not be placed on superficial tones unless the birds 
are in fine feather. 
All the Expedition specimens are passing through a com- 
plete moult, donning apparently a post-breeding garb. 
1Mon. Petrels, p. xlv. 
