466 MANUAL OF ZOOLOGY SECT. 



posterior aspect of the bone, is attached by ligament a sabre- 

 shaped scapula (scp.) which extends backwards over the ribs, 

 and includes, with the coracoid, an acute angle, the 

 coraco-scapular angle. The glenoid cavity (gl. cv.) is 

 formed in equal proportion by the two bones ; internal to 

 it the scapula is produced into an acromion process. In 

 front of the coracoids is a slender V-shaped bone, the 

 furcula (fur.) or " merrythought," the apex of which nearly 

 reaches the sternum, while each of its extremities is attached 

 by ligament to the acromion and acrocoracoid processes 

 of the corresponding side in such a way that a large 

 aperture, the foramen triosseum (f. trs.) is left between the 

 three bones of the shoulder-girdle. The furcula is a 

 membrane bone and represents fused clavicles and 

 interclavicle. 



Equally characteristic is the skeleton of the fore-limb. 

 The humerus (Fig. 264, hu) is a large strong bone, with a 

 greatly expanded head and a prominent ridge for the in- 

 sertion of the pectoral muscle. The radius (ra) is slender 

 and nearly straight, the ulna (ut) stouter and gently curved. 

 There are two large free carpals, a radiale (ra) and an 

 ulnare (uF\ and articulating with these is a bone called the 

 carpo-metacarpus (cp.mtcp) consisting of two rods, that on 

 the preaxial side strong and nearly straight, that on the 

 postaxial side slender and curved, fused with one another at 

 both their proximal and distal ends ; the proximal end is 

 produced pre-axially into an outstanding step-like process. 

 The study of development shows that this bone is formed 

 by the union of the distal carpals with three metacarpals 

 (Fig. 265), the second and third of which are the two rod- 

 like portions of the bone, the first, the step-like projection. 

 Articulating with the first metacarpal is a single pointed 

 phalanx (ph. /) ; the second metacarpal bears two phalanges, 



