The British Guiana Museum. 253 
double muscles which are continued behind and above 
the skull where they are inserted. The feet are very 
small, reduced and weak, and are only adapted for 
supporting the bird when it perches. The tail consists of 
only ten feathers, some of which may be extremely elon- 
gated. The wings contain only ten primary feathers, 
and the muscles working the wings are extremely large, 
and, in correspondence with this, the keel of the sternum 
or breast-bone is extremely strong, and high. Their eggs 
are two in number and very small, and the nest is beauti- 
fully construfted. The humming-birds are found only in 
the North and South American regions, not having 
extended to Europe, Asia or Africa. In the East Indies, 
they are represented by the sun-birds, which in external 
appearance closely resemble them, but which, how- 
ever, are quite different in internal structure. They are, 
in spite of their elongated beaks, closely allied to the 
swifts in stru&ure, and, in the young state, when the 
beak is not yet grown, the resemblance is strikingly 
evident, even in the form of the beak. 
Of the family of the swifts (Cypseli) , a specimen of the 
large swift (Hemiprocne) is shewn in the flat-case (3) in 
the middle. In this family the bill is short, and very wide 
in the gape ; the wings are extremely powerful ; the 
legs very short and weak, and all the four toes are directed 
forwards. These birds avoid the ground, and perch 
on the lofty branches of trees. They are widely distri- 
buted throughout the world. 
Of the widely spread family of the cuckoos (Cuculidde) 
a specimen is shewn, in the flat-case (3) in the middle, of 
the American cuckoo (Piaya) , a bird of a ruddy-brown 
colour above, ashy-grey below, with white bars on the 
KK 
