1889. ] Lucas, the Main Divisions of the Swifts. II 
While retaining the general characters of the Swifts, the shoulder 
girdle of Dexdrochelidon departs widely from the typical Cypse- 
line pattern. The xiphoid margin of the sternum instead of being 
convex is slightly concave, and instead of being imperforate 
presents on either side. a subtriangular fenestra occupying the 
place of the notch found in Passerine birds. ‘These fenestra are 
not to be confounded with the sternal vacuities so constantly found 
in the Swifts, for large, irregular fenestra are present in the body 
of the sternum ; but the marginal fenestre are such as would be 
formed were the external xiphoid process of a Passerine bird united 
with the body of the sternum by a bar of bone. The outline of the 
carina is more convex than in any of the other Swifts, and recalls 
the Caprimulgine sternum. 
The coracoid is moderately long, much longer than in any of 
the allied forms, its length, in comparison with the total length of 
the sternum, being 58% in D. wallacez, and 74% 7x D. mystacea, 
while in MWicropus apus it is 3%, in Collocalia fuciphaga ?35, 
and in Chetura pelagica pfy. The furcula is also longer and 
the hypoclidium better developed than in other Swifts, the furcula 
resting upon the anterior edge of the carina. The scapula is more 
decurved than in any other Swift except Collocalzia, but ex- 
perience with other forms shows that the scapula has but slight 
taxonomic value. 
Unfortunately there is no humerus among the bones in my 
possession, but from the proportions of the other bones of the 
wing it would not be surprising if the humerus should prove to be 
longer and less strongly marked than the usual Cypseline pattern.* 
The radius and ulna, instead of being considerably shorter than 
the second metacarpal, are considerably longer, while they are 
also more concave toward one another than in other Swifts. The 
*Since the above was written, Dr. W. K. Parker has very kindly sent me for examin- 
ation askeleton of D. coronata. This corresponds in the respective portions of its 
skeleton with the species already examined, while the humerus proves to be as sur- 
mised, much more slender and much less rugose than in the other Swifts. 
The differences of proportional length between the wing bones of J/icropus apus and 
Dendrochelidon mystacea can be well expressed in figures by calling the length of the 
metacarpals oo. 
They are as follows: 
M., apus. D. mystacea. Chetura.  Collocalia. 
Metacarpals 100 100 100 100 
Radius 76 IIo 75 88 
Humerus 56 95 60 63 
