82 INTRODUCTION. 



last true rodent ; and theimplacental, 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, 

 solJered together, or wanting. 



