178 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, 
millim. transversely ; the arrest of the keel, behind, is not seen in 
Caprimulgus. 
The scapule of Steatornis (Plate XVIII. fig. 8, sc.) are 50 
millim. long, 5 millim. broad at their widest part, and 3 miilim. in 
the middle; they are elegantly xiphoid, and have a sharp decurved 
point. The coracoids (cr.) are also long; their length is 38 millim., 
the upper, or fifth, 8 millim.; at their largest (epicoracoid) angular 
expansion they are 15 millim. across, and only 3°5 millim. in the 
middle of the elegant and slightly sigmoid shaft; the clavicular 
process (root of precoracoid) is very small. 
The furcula (/r.) is strong and U-shaped; in a straight line from 
the apex to their lower junction the rami measure 37 millim. ; their 
average growth is 3 millim.; it is very uniform. 
There is a smallinterclavicular knob (i.c/.), 2 millim. high, behind 
the junction of the rami. 
The aborted “‘precoracoid”’ segment of cartilage has added very 
little to the apex of each ramus. 
The curve of the rami (cl.) is great, and the roundness of the space 
where they meet below is perfect; it is a typical U-shaped furcula. 
This is one of the most common forms of the furcula, not only in 
the great and varied group of the Coceygomorphe, but also in Birds 
generally. Outside the Passerines, in the Arboreal groups, this 
form is very common, e.g. in Trochilidz, Cypselide, and in Po- 
dargus, Eurystomus, and Bucerotide ; whilst Rhamphastos, with its 
divided rami, and the Picide and most of the Alcedinide, have Pas- 
serine apices to their rami, that is they are dilated or bilobate. 
V. Phe Wing. 
The extreme slenderness of the bones forming the wing of Stea- 
tornis (Plate XX. fig. 1) is in great contrast with what we see in the 
Bucerotidee, with their dilated and cellular bones. 
The relative length, however, of the three regions is very similar 
in both, the humerus and the manus being both very short, the eu- 
bitus very long. 
Thus, although this bird, like the Swifts and Humming-birds, has 
its wings twice as large as iis legs, it is not a Macrochire ; its hand 
is very small. 
The following measurements of the region in several long-winged 
birds will make this plain; the meaning of these differences will be 
self-evident when the mode of flight of each type is considered :— 
Humerus. Ulna. Manus. 
millim. millim. millim. 
Steatornis caripensis .... 72 106 82 
Buceros ruficollis ...... 102 147 85 
Caprimulgus europeus .. 35 45 50 
Cypselus apus ........ 12 18 43 
Strix flammea.........-. 80 88 75 
Larus canus ......00+. 92 102 102 
It will be seen at once that the intensest specialization has 
occurred in the Swift, where the humerus is only two thirds the 
