OSTEOLOGY OF BIRDS 189 



degree." It is a well known fact that it is a rare thing to come 

 across a perfectly symmetrical sternum from a common domestic 

 fowl, whereas it is truly an elegantly fashioned bone, not only 

 in G . b a n k i V a , but in many of its allies as the grouse and 

 partridges. Much of this is due to the graceful sweep of its deep 

 keel, its lofty costal processes, its widespreading and delicate 

 xiphoidal limbs ; and its handsome manubrium, transversely pierced 

 at its base by a communicating foramen connecting the costal 

 grooves [see fig. 8, 9]. In G. bankiva, too, the sternum 

 is highly pneumatic, and perforations for the admission of air 

 into its substance are to be found in the little valleys among the 

 facets for the haemapophyses upon the costal borders ; and a more 

 extensive one upon the far anterior aspect of its thoracic surface, 

 or in the median, longitudinal furrow behind these latter. 



Not content with simple appearances, Darwin even went further 

 than I have hinted at in the last paragraph, for he made many pro- 

 portional measurements, among depth of carina, length of bone, 

 etc., etc.. for our present subject as compared with the domesticated 

 species ; and to those comparisons I will add here the dififerences in 

 size of the bone in the adult male and female — data which, for 

 the end he had in view at the time, were not especially called for, 

 and consequently not presented. These measurements I will offer 

 in another table, after we have briefly considered the shoulder girdle. 



Let any one take the pains to compare Parker's excellent figure 

 of the pectoral arch chosen from a common barnyard fowl, and 

 presented us in the ninth edition of the Encyclopaedia Britannica 

 [3:720], with my drawing here given [fig. 16]. of the same 

 parts for G . bankiva. and it will not be hard for him to admit 

 that the bones of the wild fowl have a more delicate, graceful, and 

 withal, elegant appearance, than those of the long domesticated 

 species. And in truth so it is. In G . bankiva. the liiubs of 

 the OS furcula are slender and subcylindrical, more especially so in 

 the hen where this bone is a very delicate structure, while its cora- 

 coidal ends are but moderately expanded in either sex. Chiefly, 

 however, is to be noticed its large, subtriangular hypocleidium, 

 with its salient angles nicely rounded ofif, and its broader moiety 

 pendant. 



A coracoid possesses but a fairly tuberous head, with its summit 

 hooked over mesiad, so that when the arch is articulated in situ, 

 it largely shares in forming the " tendinal canal," and allows the 

 corresponding head of the os furcula to rest against it, but not the 



