IO Lucas, the Main Divisions of the Swifts. [January 
is comparatively wide, slightly suggesting Caprzmulgus in its 
outline. Viewed from below the elongation of the rostrum is very 
noticeable while the pre-maxillaries are seen to run well back- 
ward, thus contrasting with the other Swifts and once more sug- 
gesting Caprimulgus. 
Dendrochelidon has the characteristic unciform maxillo- 
palatines of the Swifts, but the palatines and vomer differ totally 
from the Cypseline pattern. The pre-palatine bar is narrow, in- 
stead of wide, the external palatine notch is wanting, and the 
trans-palatine portion is entirely different in shape from that of 
the other Swifts, being not unlike Caprimu/lgus. The anteriorly 
T-shaped vomer of the other Swifts is replaced by a vomer that 
is scarcely expanded at all distally. 
Ventral aspect of crania of 1. Antrostomus vociferus, 2. Dendrochelidon mystacea, 3. 
Chetura pelagica, all enlarged to the same absolute size. 
v, vomer; mx, maxillo-palatine; 7, prepalatine; ee, ecto-ethmoid; 7//, trans- 
palatine; fo, pterygoid; g, quadrate; s, sphenoid; 4¢, basi-temporal. 
One maxillo-palatine is omitted to better show the vomer. 
Owing to foreshortening the length of the rostral portion of the skull of Dendrochel- 
zdon is apparently not so great asit is in reality. 
The sphenoid of Denxdrochelidon partakes of the general elon- 
gation of the skull, and the articulations of the pterygoids with 
the sphenoid are brought well forward, and form a rather sharp 
angle with one another. This is a departure from the Cypseline 
structure, in which the pterygoids are closely applied to the basi- 
temporal, and a step toward the Passerine arrangement. 
