108 CONNECTION OF MEMBERS WITH VERTEBRAL COLUMN. 



Fio. 61. STERNAL APPARATUS OK 

 ORNITHORHYNCUS. 



attain a very high degree of development ; and their arrange- 

 ment more resembles that which is found in Lizards and Birds, 

 than that which prevails among ordinary Mammals. A bone in 

 the form of a Y (e?, Fig. 61) is applied on the upper or anterior 



extremity of the sternum, s, and 

 sends its two branches to the two 

 scapulae, in the same manner as 

 the furcula or merry-thought of 

 Birds (ANIM. PIIYSIOL 89); 

 two pieces, cr>, situated beneath 

 this fork-like pair of clavicles, 

 represent the coracoid bone of 

 Birds and Lizards, which in ordi- 

 nary Mammals is but a small 

 projection from the scapula, not 

 nearly long enough to reach the 

 sternum ; and finally the scapula 

 itself, o, instead of terminating in 

 the cavity, ^, which lodges the 



head of the humerus, is prolonged beyond it, and comes to meet the 

 sternum, s ; thus having three bony connections, where in 

 many Mammals there is none at all, and in no others more than 

 one. The functions of the lower or 

 hinder members vary less than those 

 of the upper ; hence the mode in which 

 they are connected with the trunk 

 is much more uniform, except amongst 

 the Cetacea, in which they exist only 

 in a rudimentary state. The bones of 

 the hip are always immovably fixed 

 to the sacrum, and are united together 

 at their lower extremities, so as to 

 form a complete ring more or less deep, Plo 62 ~Lp EIvr8 OF THK ECHIDNA . 



termed the pelvis Or baSOn. The <*. base of the vertebral column: , 

 ..... . . iliac bone ; m, marsupial bone ; 



form and size of this bony circle vary /, cavit y f or the head of the femur 



greatly; and it may be remarked that, 



when other things are equal, the vertical position in which the 



