82 INTRODUCTION. 



last true rodent ; and the implacental, the marsupia- 

 lia, and monotremata. They have all the upper jaw 

 fixed to the skull, and the lower, formed of only two 

 pieces, is articulated to the temporal bones. The 

 neck is composed of seven vertebrae ; * those of the 

 back and loins vary occasionally in the same species ; 

 the anterior ribs are secured to the sternum, or breast 

 bone, by cartilaginous processes ; the anterior extre- 

 mities commence with a shoulder blade, not articu- 

 lated, but suspended between the muscles, and often 

 resting on the sternum, by means of the clavicle on 

 each side : it is continued by an arm, forearm, and 

 a hand ; the hand is formed of two rows of bones, 

 (the carpus), of another row (the metacarpus), and 

 of fingers, each consisting of two or three joints, 

 called phalanges, t 



If we except cetacea, or the whale tribe, all mam- 

 malia have the basin or pelvis attached to the spine, 

 the pubes forming the anterior, and the ilia, ischia, 

 sacrum, and coccyx ; the lateral and posterior parts, 

 where the three first-named bones of the pelvis unite 

 on each side, is the cavity wherein the femur or thigh 

 bone is articulated : to the former are attached the 

 leg bones (tibia and fibula), in most cases distinct, 

 succeeded by those composing the foot, which cor- 

 respond to the bones of the hand ; namely, a tarsus, 



* With the exception of the three-toed sloth, which has 

 nine. In cetacea, though seven, they are united into one by 

 anchilosis. 



t Several of these bones are, in different tribes of animals, 

 sol'Jered together, or wanting. 



