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Show 178 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, millim. transversely ; the arrest of the keel, behind, is not seen in Caprimulgus. The scapulae of Steatornis (Plate XVIII. fig. 8, sc.) are 50 millim. long, 5 millim. broad at their widest part, and 3 millim. 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 (//*.) 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 small interclavicular knob (i.cl.), 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 Coccygomorphae, but also in Birds generally. Outside the Passerines, in the Arboreal groups, this form is very common, e. g. iu Trochilidae, Cypselidae, and in Podargus, Eurystomus, and Bucerotidae ; whilst Rhamphastos, with its divided rami, and the Picidae and most of the Alcedinidae, have Passerine apices to their rami, that is they are dilated or bilobate. V. The Wing. The extreme slenderness of the bones forming the wing of Steatornis (Plate XX. fig. 1) is in great contrast with what we see in the Bucerotidae, 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 cubitus very long. Thus, although this bird, like the Swifts and Humming-birds, has its wings twice as large as its 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 europceus 35 45 50 Cypselus apus 12 18 43 Strix flammea 80 88 75 Larus canus 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 |