234 ZOOLOGY. 



progression Mini not prehension, the collar bones are either 

 altogether wanting or ivdueed to mere vestiges. Sonic very 

 singular and anomalous animals, also mammals, no doubt, 

 ditl'cr widely in many respects from the ordinary organi- 

 zation, and in none more than what concerns the structure of 

 the shoulder : we allude to the ornithorhynchus paradoxus 

 and echidna setosa, of New Holland. In these the skeleton 

 of the shoulder more resembles what we find in lizards and 

 in birds than in mammals. 



The arrangement of the bones of the shoulder in these 

 singular animals will be best understood by a reference to 

 Fig. 182, in which d points to two bones on each side (of 

 which one is not represented here) corresponding to the 

 usual collar bones of mammals; a points to the scapula; 

 h to the cavity for the articulation of the head of the hu- 

 merus ; o the prolongation of the scapula to the sternum, 

 analogous to the coracoid clavicle of birds ; co an osseous 

 piece, the analogue of which has not been determined; s and c 

 point to the ribs. The meaning of this complexity of the 

 shoulder in this class of animals has never yet been ex- 

 plained. 



The functions of the basilar portion of the skeleton of the 

 abdominal or hinder limbs, varies less than does that of the 

 pectoral. In the cetacea, also in the dugong and lamantin, 



a co d 



Fig. 182. Fig. 183. 



the pelvis is reduced to a mere fragment ; in other mammals, 

 the bones of the haunches (/) articulate in an immovable 



