1889.] Lucas, the Main Drvistons of the Swifts. 9 
it is impossible for me to coincide in his view of the relationship of 
Collocalia, although fully agreeing with him in regard to its 
being in every point strictly Cypseline. Collocalza, for whose 
skeleton I am indebted to my friend Mr. C. F. Adams, is a 
member of the Cheturine group of Swifts, and so nearly resembles 
in structure our common Chimney Swift that it would be difficult 
on structural grounds to separate them generically. 
The members of the genus Dexdrochelidon on the other hand 
stand by themselves among the Swifts, the characters separating 
them from their relatives, as represented by AZ¢cropus apus, M. 
subfurcatus, Panyptila saxatilis, Chetura pelagica, and Col- 
localia fuctphaga are well marked. An entire skeleton of Den- 
drochelidon is unfortunately not at hand, but Prof. Alfred Newton 
has most kindly loaned me a skull and sternum of LD. mystacea 
and two sterna of J. wallacez, which with some wing and leg 
bones furnish an abundance of good differential characters.* The 
skull alone would be quite sufficient to separate Dendrochelidon 
from the other Swifts and the other bones furnish strong corro- 
borative testimony. 
Viewing the cranium of Denxdrochelidon from its dorsal aspect, 
the rostral portion is seen to be both narrower and longer than in 
either Micropus, Panyptila, Chetura, or Collocalia. The mass 
of the ecto-ethmoid, so prominent in other Swifts, does not project 
beyond the outline of the frontals. There is no lachrymal in any 
of the skulls of Dezdrochelidon at my disposal, though this little 
bone is present in Micropus subfurcatus and Collocalia fuct- 
phaga. 
A decided structural difference exists between Dexdrochelidon 
and the other Swifts in the frontal region from the fact that in 
Dendrochelidon the nasals are posteriorly narrow, and simply 
-abut against the frontals, while in the other Swifts an external 
process of the wide nasals is carried upward and backward, over- 
lying the frontals. In this respect the adult Dexdrochel¢don 
much resembles the younger stages of other Swifts, in which the 
external and internal processes of the nasal ossify first, forming a 
crescentic bar of bone bounding the nasal opening. Later on the 
ascending process ossifies, forming a tri-radiate bone, extremely 
well marked in Paexyptzla. The interorbital portion of the frontals 
*See, however, foot-note on page It. 
