APPENDICULAR SKELETON 



229 



upper iliac and a ventral ischio-pubic region. In the cartilage 

 stage each girdle is perforated ventral to the articulation of the 

 free hmb for nerves going to the appendage, a supracoracoid foramen 

 in either half of the pectoral girdle, an obturator foramen in the pubic 

 (anterior) part of the ischio-pubic region. 



Several bones may ossify in either half of the cartilage girdles. 

 One extreme of this results in the formation of the following bones in 

 either half: Pectoral girdle, dorsal to the glenoid region is a scapula 

 (shoulder blade), extending upwards from the glenoid, its upper part 

 often persisting as a separate bone, the suprascapula. In the cora- 

 coid region is an anterior pre- (or pro-) coracoid and a more posterior 





Fig. 242. — Diagram of Tetrapod girdles and appendages, posterior vie-n". Upper 

 letters, pectoral appendage; lower, pelvic appendage; a, acetabulum; c. carpus; co, 

 coracoid; ec, epicoracoid (no equivalent in pelvis);/, femur; fi, fibula; g, glenoid fossa; 

 /;, humerus; i, ilium; is, ischium; mc, metacarpus; mt, metatarsus; p, pubis; pc, pre- 

 coracoid; ph, phalanges, numbered; r, radius; 5, scapula; 5S, suprascapula (no equivalent 

 in pelvis); t, tarsus; tb, tibia; u, ulna; I-V, digits. 



coracoid bone (metacoracoid), these meeting in the glenoid region 

 and having a considerable gap (coracoid fenestra) between them. 

 The medial (ventral) ends of precoracoid and coracoid may be 

 united by an epicoracoid cartilage or bone. With ossification the 

 supracoracoid foramen is usually included in the coracoid bone.^ 

 To this pectoral girdle of cartilage origin, bones arising in mem- 

 brane may be added, thus forming a secondary girdle, reinforcing 

 or even replacing parts of the cartilage girdle. These are best 

 1 The nomenclature of the coracoidal elements is confused. The name coracoid was 

 first given to a process of the human scapula which was soon recognized as arising from a 

 centre apart from the scapula. Later an additional centre was found in the coracoid of 

 mammals, all three centres persisting as separate bones in some species. Adult Mono- 

 tremes have two distinct bones (fig. 273) in the same position as the rudimentary 

 elements of higher mammals, and Cuvier applied the name coracoid to the posterior 

 of these, calling the anterior the epicoracoid. Amphibia and many reptiles having two 

 bones in the same relative position as the Monotreme coracoid and epicoracoid, the 



