1 96 VERTEBRATE ZOOLOGY 



The distal division is made up of the wrist and the hand. The 

 carpal, or wrist, bones are much modified, but two free bones being 

 present, the radial and the ulnar, which are at the distal ends of 

 the radius and ulna respectively, the other carpals being fused with 

 the carpo-metacarpus. 



The bones of the hand fall into two groups, the proximal carpo- 

 metacarpus and the distal digits. The carpo-metacarpus is a large 

 arched bone, which is formed by the fusion of the distal carpal 

 bones with the first, second, and third metacarpals. The digits 

 are also three in number. The first, or thumb, is short and posses- 

 ses free movement; it is situated at the base of the carpo- 

 metacarpus and consists of two phalanges, the distal phalanx being 

 very small. The second digit is the longest and has three pha- 

 langes ; the third has a single phalanx. 



Exercise 37. Draw the bones of the wing. 



The Posterior Extremities. These consist of the pelvic girdle 

 and the legs. The pelvic girdle is very large and is firmly anky- 

 losed with fourteen or fifteen vertebrae, forming a solid support 

 for the legs. The pelvic girdle is composed of a right and a left 

 innominate bone, each of which has been formed by the fusion 

 of three bones: the ilium, ischium, and pubis. At the meeting- 

 point of these bones is the acetabulum, the depression in which 

 the head of the femur articulates. 



The ilium is the largest of the pelvic bones. It is a large, flat 

 bone, dorsal in position, and is fused along its entire length with 

 the vertebral column; it is divided into two parts, an anterior 

 and a posterior, the former of which is concave dorsally and the 

 latter convex dorsally. 



The ischium and the pubis are both ventral to the acetabulum, 

 the latter being anterior and ventral to the former. The ischium 

 is larger than the pubis, and is separated from the ilium at its 

 forward end by a large opening, the iliosciatic foramen. The pubis 

 is long and slender and is separated from the ischium by the long 

 and narrow obturator foramen. 



Exercise 38. Draw the dorsal and the lateral aspect of the innominate 

 bone. 



