782 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
in a general way and also of the color of the under parts. The under parts of cerulea are fully as dark 
as the back, which (in an old skin collected by T. R. Peale, Dog Island, Low Archipelago) is more 
ashy than that of saxatilis. 
Procelsterna saxatilis shows its closer kinship with cinerea in the light lower parts and light gray 
wedges on the four outer primaries; but, as mentioned above, it is smaller than cinerea, with con- 
spicuously shorter wing and shorter and slenderer bill. The under wing-coverts are pearl-gray instead 
of white, and the breast, sides, and lower tail coverts are decidedly gray, whereas in cinerea the lower 
parts are almost white, and entirely so on the belly. The general tone of the plumage of cinerea is 
ashy, but in saxatilis it is somewhat bluish. 
While the geographical distribution of the present form is very restricted, so far as known, being 
found on French Frigate Shoals, Necker, and Bird islands only, that of its nearest relative cinerea is 
rather wide, ranging over “Australian and New Zealand seas, Lord Howe, Norfolk, and neighboring 
islands, the Kermadec group, also the islet of San Ambrosio, which is nearest to the coast of Chile, but 
lies outside the cold Antarctic current,” and Eua, Friendly Islands. (L. c., p. 136.) 
A very interesting point is the fact that Procelsterna cerulea (Bennett) ranges in between the two 
forms, so that in addition to being far removed from its nearest ally, saxatilis is further segregated by 
the intervention of this less closely related species. Cerulea is distributed over “central Polynesia, 
Paumotu or Low Archipelago, the Marquesas, the Society to the Ellice islands, the Phoenix group, 
and the Fannings (Christmas I.), a little north of the Equator.” (L. c., p. 134.) 
A redescription of Procelsterna saxatilis is here added for the sake of completeness: 
Type No. 188651, U. S. N. M., adult male. Bill black; pileum and fore part of cervix, lores, chin, 
and throat clear light gray (about No. 8 or 9 of Ridgway’s nomenclature), shading to darker (between 
French gray and cinereous)" on nape, cheeks and sides of neck, and passing into a trifle lighter gray 
(No. 7) on sides, hind part of jugulum, breast, flanks, and lower tail coverts. Fore part of jugulum and 
the abdomen pure white, blending into surrounding gray of sides and breast. Breast almost as pale 
as the pileum, but becomes gradually darker on sides, sides of neck, shoulders, and malar region, 
inclosing the conspicuously lighter throat and white jugular patch. An orbital ring is black in 
anterior two-thirds of upper, in forward and first third of lower parts, and pure white for the 
.remainder. The black and white are conspicuous, being from 1 to 2 millimeters wide. There is 
a small white area just above black on “eyebrow.” The gray of the nape and hind neck and 
shoulders shades gradually into a darker and less bluish gray over the mantle (about gray No. 5 or 
slightly darker), which darkens into a decidedly ashy gray (between slate gray and mouse gray) on 
wing coverts. Secondaries conspicuously edged with white. The feathers of the mantle are vermicu- 
lated with almost obsolete bars of lighter gray (present also in cinerea and cerulea) which show plainly 
in favorable lights. Primaries dark slate color, an indistinct light gray “wedge” on inner web of first 
three primaries (reaching to within 25 millimeters of tip on first), less conspicuous on fourth, and 
represented on remainder by an indistinct lighter edging. Shafts of primaries very dark sepia. Under 
wing coverts pearl gray, whitish at bend of wing. Rump, upper tail coverts, and rectrices like mantle. 
Inner web of each rectrix edged with pale gray distally, becoming almost white proximally (less 
extended than in cinerea) . Legs in life a dull sepia black, paler toward and on tibiae and toes; webs 
creamy flesh color, rather lifeless, with an indefinite edging of sepia next to toes. Iris deep sepia, 
pupil black. Measurements of type in millimeters: Length, in flesh 285; wing 186: tail 113; culmen 
26; depth of bill at nostril (post, end) 5.5; bill from nostril 17.5; tarsus 25; middle toe 32. 
Adult female, No. 188652, U. S. N. M. In color like the male, but a trifle smaller (for size see table 
of measurements). 
Juvenal plumage, No. 188653, U. S. N. M. , female immature. The upper parts are as a whole darker; 
the pileum of dark feathers is edged with light gray, giving a mottled appearance. The mantle is darker 
and more ashy than adult, lacking faint bars, except on longest tertials. Inner tertials, and upper tail 
coverts edged with light gray. Lower parts, as a whole, lighter than adult, being white except an illy 
defined band across breast and on throat, which are gray. Sides of head and neck darker than adult. 
Black portion of orbital ring much wider and more conspicuous than white. White area over eye as 
in adult. Malar stripe white. Measurements in millimeters: Wing 157; tail 80; culmen 17; tarsus 23. 
Nestling, recently hatched (male), No. 188654, U. S. N. M. Completely covered with soft down. 
Pure white below. Crown white; sides and back of neck very pale buff. Ends of wings white; inner 
portion of alar and the humeral and spinal tracts brownish gray (down white at tips and brownish 
gray below). Feet greenish gray; bill blackish. 
