24 



solidly cemented together by their excrement. It probably affords 

 them diversion during the monotonous period of incubation to break 

 off all the twigs within reach of their bill, and to drop them under 

 their nests. These mounds furnish evidence of the nests being occupied 

 for several successive years ; for the lean bushes could not furnish a 

 sufficient amount of twigs to build them up in a single breeding-season. 

 One is the usual number of eggs, though sometimes two were found 

 in the same nest. They are somewhat larger, but in every other respect 

 similar to the eggs of Siila leucogastra. 



SULA CYANOPS, Sundev. [Kos. 67315, 67310]. 



Dysporus cyanops, Sundev., Phys. Tidskr. Lund., 1837, pt. 5. 

 Sula cyanops, Sundev., Isis, 1842, 858. 

 Sula personata, Gould, Proc. Zool. Soc. London, 1846, 21. 

 Sula piscator, Peale, U. S. Espl. Exped., Orn., 1848, 273. 



Locality: Christmas Island. One specimen in immature plumage. ' 

 The whole of the upper surface of the body dark brown, mottled with 

 white. The brown color of the back and upper surface of the wings 

 has a grayish tinge ; the head and neck all around dark brown, as in 

 S. leucogastra, except that the dark color does not extend as far down 

 on the breast as in the latter. The general system of coloration is 

 much the same as in leucogastra. If we are to learn anything from 

 the transitional plumages of birds, may it not be that they show ug the 

 parent types from which the species are progressively developed? Many 

 instances might be mentioned where the immature plumages of birds 

 represent the perfect plumage of some closely allied species. 



S. cyanops were breeding on Christmas Island. They were not very 

 abundant. They build no nest, but scratch a slight concavity in the 

 fine coral sand, where the egg is deposited. All of those observed 

 breeding on Christmas Island were in full adult plumage. One, a young 

 bird in the leucogastra style of dress, was seen nesting on Palmyra. Its 

 nest was on the ground, and was well constructed of grass. This is 

 another exemplification of the rule observed all along of the different 

 habits of the same species of birds on these two islands. 



GEACULID^. 



GEACULUS BRASILIANDS, {Gm.) Gray [No. 67369]. 



ProceJlaria hrasUiana, Gm., Syst. Nat., i, 1788, 564. 

 Puffinus hrasiliensis, Br., Av., vi, 1760, 138, sp. 4. 



