1905.] 



OSTEOLOGY OF THE EURYLJ^MID^. 



47 



is long, slender, gently arched, and bears a large hypocleidenm, 

 roughly quadi-angular in form, and articulating with the anterior 

 edge of the carina. The free ends of the furcula are exjoanded to 

 form flat plates articulating with the acrocoracoid, procoracoid, and 

 acromion process of the scapula (text-fig. 14), thus enclosing the 

 foratnen triosseimi. 



In the form of the sternum and shoulder-girdle the Eurylsemidfe 

 closely resemble the Ootingida?, especially in the form of the spina 

 externa, which is simple, and thereby difiers from the typical 

 Passerine form wherein it is forked. In the Euryleemida3 this 

 process is more or less spike-shaped, whereas in the Cotingidse it 

 appears to be generally flabellate. In Chasmorhynchus the 

 posterior sternal notches are not so deep as in the Eurylsemidse. 

 The hypocleidenm articulates nearer the antero-ventral angle of 

 the carina ; and the coracoids do not develop the internal basal 

 flange found in the Eurylaemidse. 



Text-fio-. 14. 



ccc /- W' 



/' 



Poitiou of the slioulder-girdle of Calyptomena, to show the meeting-point of the 

 scapula, coracoid, and clavicle, forming the inner wall of the foramen triosseum, 



sc, scapula ; ac, acrocoracoid ; _/., furcula. 



In the relations of the articulations between the procoracoid, 

 furcula, and scapula, where these iinite to form the foramen 

 triosseum, the Eurylfemidse are distinctly Passerine, though this 

 arrangement also obtains among the Picidte — a fact of some 

 significance. 



In Caly2Jtomena, for instance, the acromion process of the scapula 

 extends downwards along the anterior border of the free edge of 

 the procoracoid, and aifords an articular surface cephalad, for the 

 posterior angle of the expanded free end of the furcula. In 

 Chasmorhynchus this articulation for the furcula is markedly 

 increased ; and this increase apparently reaches its maximum in 

 the Oorvidse, where the acromion forms a long beam-like roof 

 to the foramen triosseum, and a very extensive articular surface 

 for the furcula. 



