OSSEOUS SYSTEM. 77 



strongest in the Pigeons, Swifts (Cypselus), and the Pratincoles (Gla- 

 reola). The keel is very broad in the Crane, from its being hollowed 

 out to receive a convolution of the trachea. The anterior median 

 process is mostly furcate in the Passerine birds and also in the Par- 

 rots, but it is small and undivided in the Rapaces. The sternum is 

 without any openings upon its posterior edge in Trochilus, C.ypselus, 

 and the Brevipennes. A pair of slight notches is found in Carbo, 

 Caprimulgus, Podiceps. The Diurnal birds of Prey have simply a 

 pair of round openings, which in old individuals occasionally dis- 

 appear. Most Parrots and the Picariae have similar openings, but 

 a sternum of smaller size. The Passeres have a pair of simple but 

 often deep incisures, which are still more strongly developed in many 

 Grallse and Palmipedes. In the Owls there are two small notches 

 and processes upon either side of the middle of the posterior border, 

 as also in many Scansores and Picariae, and many of the Grallse and 

 Palmipedes, where they are often larger. The Gallinae have four 

 very deep notches, especially the internal pair, and very long abdom- 

 inal processes, so that their sternum contains the least extent of bone. 

 In the Pigeons the sternum is similar in character, though the exter- 

 nal notch is larger. In the Divers (Colymbus) the middle posterior 

 portion of the sternum is very long. 



The Scapular Arch of birds consists of a narrow, somewhat 

 curved, and long scapula, which covers the ribs posteriorly from 

 above, and is united anteriorly by fibre-cartilage with the coracoid 

 bone. The latter, which has been called also the posterior clavi- 

 cular bone, but which is regarded by some anatomists as an in- 

 creased development of the coracoid process of the scapula, becomes 

 broader inferiorly toward the sternum, and is united to the anterior 

 edge of that bone by a tense capsular ligament. There is found 

 very generally a second anterior V-shaped clavicular bone, com- 

 monly called the " merry-thought" bone (furcula), the prongs of 

 which converging downward and backward, are, with scarcely 

 any exception, blended together, and frequently project into a pro- 

 cess, which is United by ligament to the anterior apex of the sternal 

 keel ; more rarely a joint is formed in this situation which subse- 

 quently becomes obliterated by the formation of bony tissue. All 

 these bones exhibit, with the exception of the Struthious birds, no 

 very remarkable differences. In the Penguin, however, the sca- 

 pula is very straight, and unusually broad at its posterior extrem- 

 ity ; in the Woodpeckers it is bent behind in the form of a hook. 

 The furcula is, in the Diurnal birds of Prey, very much divaricated, 



