OSTEOLOGY OF BIRDS 225 



When the girdle is articulated in situ, the clavicular extremities of 

 the os fnrcula quite extensively meet the . scapulae. The hypo- 

 cleidium of the former is not very large [pi. 4, fig. 10]. 



Coming next to the sternum, we find that although it has the 

 general pattern of that bone as we see it in the typical fowls, it yet 

 has a distinctive form of its own. It is shorter and somewhat 

 broader than the ordinary gallinaceous sternum, and the large, stout 

 costal processes are directed backward, rather than forward as they 

 are in the grouse. The forepart of the sternal body is rather broad 

 and tapers behind to a point. Either outer xiphoidal process is 

 much as we find it in the fowl, but the inner pair is very slender, 

 and carried to sharp points behind. A large central foramen 

 is seen upon its upper side, at the base of the manubrium, and it 

 communicates with that other foraminal opening which pierces the 

 manubrium transversely. 



Some very interesting points are found to characterize the ap- 

 pendicular skeleton of Ortalis. Its pneumatic humerus has a small 

 radial crest only, and the sigmoidal curving of its shaft is pro- 

 nounced. It has a length of six centimeters, being half a centi- 

 meter longer than is the stout bowed ulna of the antibrachium. This 

 latter bone is strikingly compressed from side to side. Still more 

 interesting is the carpometacarpus, which has a length of less than 

 three centimeters, and is peculiar in that in it the indicial process 

 is entirely absent, and the shaft of the rnedius metacarpal is 

 curiously twisted and bowed. The long pollex phalanx supports a 

 good sized claw at its extremity. 



With respect to the skeleton of the pelvic limb, it is to be observed 

 that the somewhat long and slender femur is apparently nonpneu- 

 matic, and this bone has a length of 6.5 centimeters. Contrary to 

 what we find in Centrocercus, for example, its trochanter major is 

 but slightly elevated above the summit of the shaft. Tibiotarsus has 

 a length of 9.5 centimeters, and tarsometatarsus 6.4 centimeters. 

 The fibula is very slender in its proportions, and the short, chunky 

 hypotarsus of the tarsometatarsus, is grooved and pierced for the 

 passage of tendons in a manner similar to what we found in 

 Meleagris. 



One of the most remarkable structures in the economy of Ortalis 

 is its trachea, which, before passing to the lungs between the limbs 

 of the os furcula, makes a long loop outside, dipping down between 

 the pectoral muscles, and usually, I believe, upon the left side. The 

 rings, -semirings, and other parts of the trachea in the Gallinae 



