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 THE CONDOR Vol. XVII plumage of these specimens was very different from that of B. hypoleucus, these feathers being of a shade about intermediate between hair brown and seal brown. In this regard it may be appropriate to mention that I have never seen any breeding specimens of hypoleucus that are clear slaty. A slight brownish east is apparently always present, most decided on the wing quills and tips of the scapulars though the whole dorsal plumage is slightly suffused psrticulal.ly in the more worn specimens. In the case of nos. 2-7 the unicolored feathers on the sides of the body and flanks greatly outnumber the variegated ones, while with hypoleucus the exact opposite is the case. The general effect is much the same, in other words in both species the parts mentioned have a mottled appearance, but from a different cause. An individual feather in the case of craveri is, when followed up, usually found to be either dusky or white, and the mottling results from the intermingling of these feathers, but in hypoleucts the same effect'is obtained (generally speaking) by reason of the individual plume being bicolored. Aside from the smaller feet and bills no differences are discern{ble between the two birds of the year and the four adults (of B. craveri) except a more blackish east to the dorsal plumage apparently by reason of the tipping being of a slightly darker shade. Figure 27 will give a good idea of the differ- ence in shade between the breeding and fall plumage of Xantus Murrelet. To sum up the situation, nos. 2-7 may be referred to B. craveri for the fol- lowing reasons: B. hypoleucits Wing lining immaculate or nearly so. Concealed portions of dorsal plumage with faint lyrownish cast. Side of head, neck and body blackish slate. U. nicolored feathers on sides of body in minority. Worn summer feathers light slaty with faint brownish suffusion. B. craveri Wing lining heavily clouded and mottled. Concealed portions cf dorsal plumage with strong brownish cast. Sides of head, neck and body brownish slate. Unicolored feathers on sides of body in majority. Worn summer feathers about intermediate between hair brown and seal brown. The petrel colony on Los Coronados is, I am happy to state, apparently gaining in numbers each year. Messrs. Grinnell and Daggett on their visit to the Islands, August 6 and 7, 1902 (Auk, XX, 1903, pp. 27-37) make no esti- mate of the.numbers of either Socorro (Oceanodroma socorroensis) or Black (Oceanodroma melania) petrels breeding there at that time, but state that twenty-four adults of the former and four of the latter species together with many young and eggs were taken in an afternoon 's hard work. From what I have seen there the present season, it would now be rather a simple matter for two persons to obtain upwards of fifty adult Socorro Petrels in the same length of time on the same date. This refers to the main colony; but small branch colonies have sprung up wherever sufficient soil is available to burrow in. In many instances this year no burrow at all was dug, the birds simply worming their way under the dense bushes to lay their eggs. Another matter Of surprise to me is the fact that Messrs. Grinnell and Daggett found socorroetss breeding on North Island, a condition which is cer- tainly non-existent at the present time, though melana nests there in consid- erable numbers. Possibly the hordes of Cassin Auklets (Ptychoramphus aleu- ticus) which infest the island in the breeding season, as well as a mouse (Pero- myscus sp.) which also abounds there, have at last driven socorroenss to take refuge on the smaller Middle Island, which place now seems to be their sole