SKELETON OF PHOEOEHACOS INFLATTJS. 69 



The proximal end of the bone is peculiar. The acrocoracoid is almost completely 

 absent, the upper end of the bone rising scarcely at all above the scapular surface. 

 From the acrocoracoid region a ridge runs down the antero-internal border of the bone 

 and forms the inner wall of a deep channel, which is bordered externally by the 

 prominence formed by the surface for the scapula and the small procoracoid process. 

 On this descending ridge there is, at some distance from its upper end, an elongate flat 

 facet with which probably the clavicle articulated. 



The surface for the scapula is a large, deeply concave area, nearly circular in outline ; 

 below its internal border arises a small process or hook of bone (broken in the specimen 

 figured), which overhangs the groove above described and is the procoracoidal process. 



The glenoid surface is a smooth, slightly convex area, the lower border of which 

 forms a prominent overhanging lip on the postero-external side. 



The coracoid just described is one of the most remarkable bones of the skeleton. 

 Its extreme elongation and the peculiar structure of its upper end, particularly the 

 almost complete suppression of the acrocoracoid, are paralleled, so far as I am aware, 

 only in the coracoid of the flightless Aptornis. The coracoid of this bird differs, 

 however, in several important particulars, e. g. in the large size of its procoracoidal 

 process, the presence of a supracoracoid foramen, and in the complete fusion of the 

 lower extremity with the sternum. 



Fiirbringer has regarded the absence of the acrocoracoid as diagnostic of the Ratitse, 

 and has suggested that the term " Platycoracoideae " should be used for them in 

 contradistinction to the Acrocoracoidese, or Carinatfe. The occurrence of this 

 character in two such distinctly Carinate types as Aptornis and Phororhacos, however, 

 invalidates this distinction, and tends to show that the presence or absence of the 

 acrocoracoid, like that of the keel of the sternum, is in some way dependent on the loss 

 of flight, and probably also on the increase in the bulk of the body. 



The articulation with the sternum is particularly well developed, and in no bird could 

 the prominent tubercle and shelf above described be found developed to the same 

 extent. No trace of the sternum is preserved, but, judging from the coracoids, it was 

 probably of considerable size. 



Scapula. (Plate XVII. fig. 2.) 



Of the scapula no perfect specimen is preserved, but the most complete, here figured, 

 wants the distal portion of the blade only. The surface for union with the coracoid is 

 highly convex and roughly circular in outline ; it is much roughened, and the union of 

 the two bones must have been a very close one. The glenoid surface, which is slightly 

 convex, is raised on a prominence which projects considerably below the inferior border 

 of the blade. There is a very large acromium process. The portion of the blade 

 preserved is somewhat rounded externally and flat internally. 



The width of the proximal end of this bone is 30 mm. 



