2. This is not alike in all animals, for the cranium of some consists of a single bone, as in the dog; in others it is compound, as in the human subject. The female has one suture, in a circle; the male has three, meeting at the top of the head, like a triangle; and human skulls have been seen without sutures. The head is not composed of four bones, but of six; two of these are placed above the ears, and are small compared with the rest. 3. From the head the jaw-bones descend. All other animals move the lower jaw, the river-crocodile alone moves the upper jaw. In the jaws are the order of the teeth, which are bony, in some parts they are perforated, in others they are not. These are the only bones too hard to be engraved. 4. From the spinal-column, which is the point of union, originate the clavicles and ribs; the breast also is placed upon the ribs, and some of these are united, others are not, for no animal has a bone round the stomach. There are also the scapulæ upon the shoulders, and these are continued upon the arms, and those again to the hands; and in all animals with fore legs the nature of the bone is the same. 5. At the extremity of the lower part of the spinal column, and next to the hip, is the socket, and the bones of the lower extremity, with those of the thigh and leg, which are called the colenes. The ancles form a portion of these, and the part called the spur in all creatures with ancles. Continuous with these are the bones of the feet. Viviparous animals with blood and feet do not differ much in their bones, but rather by analogy, in hardness, softness, and size. Again, some of the bones contain marrow, whilst others, in the same animal, have none. 6. Some animals do not appear to have any marrow at all in their bones, as the lion, whose bones are very small and slight: or there may be marrow in a few of its bones, as in those of the thigh and fore leg; otherwise, in the lion, the bones are particularly solid, for they are sufficiently hard to emit fire like stones on concussion. The dolphin also has bones, but it has no spine, like fish. Some sanguineous animals differ partially from these, as the class of birds. In others, as fish, the bones are only analogous, for viviparous fish have a cartilaginous spine, like those which are called selachea; the oviparous fish have a spine, which is like the backbone of quadrupeds. 7. It is a peculiarity in fish that some species have small spines in the flesh separated from each other. Serpents are like fish, for their back-bone is spinous; among oviparous quadrupeds the greater animals have a bony vertebral column; the lesser have a spinous one.