THE SKELETON OF THE TURTLE. PELVIC GIRDLE. 235 



a horny claw ; those of the other digits are flattened and more 

 or less pointed. 



THE PELVIC GIRDLE. 



The pelvic girdle consists of three bones ; a dorsal bone, 

 the ilium, an anterior ventral bone, the pubis, and a pos- 

 terior ventral bone, the ischium. All three bones contribute 

 largely to the formation of the acetabulum, with which the 

 head of the femur articulates. 



The ilium is a small slightly curved bone, which unites 

 ventrally with the pubis and ischium, and extends dorsal wards 

 and J^ack wards to meet the distal ends of the sacral ribs. 



The pubis is the largest bone of the three ; its distal 

 end forms a wide bilobed plate, the inner lobe meeting its 

 fellow in a median symphysis, while the other lobe or lateral 

 process extends outwards. Attached to the symphysis in front 

 is a cartilaginous epipubis, while behind, the two pubes are 

 terminated by a wide rounded cartilaginous area. 



The ischium, the smallest bone of the three, is flattened 

 and like the pubis meets its fellow in a median symphysis. 

 A narrow band of cartilage connects the symphysis pubis with 

 the symphysis ischii, and separates the two obturator fora- 

 mina from one another. 



THE POSTERIOR LIMB. 



This is divisible into three portions, the thigh, the crus or 

 shin, and the pes. 



The thigh includes a single bone, the femur. 



The femur (fig. 40, B, 12) is a short thick bone, with a 

 prominent rounded head articulating with the acetabulum. 

 Behind this head is a deep pit, beyond which is a roughened 

 area corresponding with the great trochanter of mammals. 

 The distal end is expanded and somewhat convex. 



The bones of the crus or shin are the tibia and 

 fibula. These are both straight rod -like bones with expanded 



