SlIUl-KLUr: OslKOLOCY OK THK HlCkODIONKS. 1 S9 



([uite close to this extremity, rests against the under side of the pro- 

 jecting summit of the mesial aspect of the coracoid. The rounded 

 end of the furcula, from this point, reaches back a sufficient distance 

 to barely escape touching the mesial and up-curled side of the scap- 

 ular head, that to all intents closes the tendinal canal by bony walls ; 

 its complete closure is really effected by the short ligament that holds 

 these two bones in situ at this, their nearest point of approach. In 

 some birds, as for instance certain diurnal Raptores, the canal is closed 

 by the head of the furcula reaching the tip of the clavicular process 

 of the coracoid. From the head of the bone to the hypocleidium a 

 gradual reduction in size takes place, while the lateral compression is 

 sustained throughout, at any rate within a short distance from the latter 

 part. 



Now the hypocleidium of the clavicles in Ardea iierodias, as in other 

 Herons, consists of both an inferior and a superior process (Figs, ii 

 and 12), both being in the .same line. In our present subject the 

 upper one is the larger of the two, while their common surface an- 

 teriorly is smooth and flat. Behind, it is rounded and marked by a 

 longitudinal raised line. This latter feature \\\ Nycticorax is raised to 

 the rank of a well-developed crest, and the lower process in this bird, 

 equals the upper in length, and as a whole is comparatively slenderer 



Figure 34 gives a three-cjuartering- view of the furcula of my sj^eci- 

 men of .'^. candidissima. It will be observed that it differs in no im- 

 portant particular from Ardea, though the anterior surface of the 

 lower process of the hypocleidium is longitudinally grooved, a feature 

 which, by the way, I neglected to say, is faintly indicated in the 

 latter Heron. 



A glance at any of the figures representing this bone in the Ardeiiice, 

 is sufficient to satisfy one that it is a very different affair from the 

 corresponding part of the pectoral arch in such forms as Siila, Phala- 

 crocomx, or Pelecamis. In these latter types the united clavicles arch 

 backwards to meet the carinal angle of the sternum, here to articu- 

 late with it, or even as in Tachxpetes and very old Cormorants to 

 anchylose with it. The lower part of the furcula in Herons, is, on 

 the other hand, turned forwards from the sternum, assuming a curve 

 not often seen among birds. 



Anatomists have termed the clavicular head in birds, the epiclei- 

 dium, and this end of the bone, according to Professor Parker, ossifies 



