CHELONIAN REPTILES. 471 



tendency to lateral expansion, which exists in 

 the spinous processes of the dorsal vertebrae, 

 prevails also among those which contribute to 

 form the skull. The parietal bones, which re- 

 present the spinous processes of the second 

 cranial vertebra, after having performed their 

 primary office of protecting the hemispheres of 

 the brain by closing over them, still proceed in 

 their developement, forming first a crest on the 

 upper part of the real cranium, and then sepa- 

 rating to the right and left, and expanding hori- 

 zontally into the upper roof (p, p) already men- 

 tioned, for the protection of the temporal muscles 

 This great breadth of the head in the turtle gives 

 the animal an aspect of superior intelligence, to 

 which character, from the really diminutive size 

 of its brain, it is in no respect entitled. As. the 

 turtle is unable to withdraw its head within the 

 carapace, such extraordinary protection appears 

 to have been necessary : for it is not met Avith 

 in the tortoise, which has a carapace sufficiently 

 capacious to give shelter to the head whenever 

 occasion may require.* 



This arrangement of the expanded spinous 

 processes and ribs gives rise to a singular inver- 

 sion in the position of the scapula ; for it is here 



* The analogy of the spine of the occipital bone with that of 

 a vertebra is further shown by this bone extending backwards to 

 a considerable length, exactly in the manner of the spinous pro- 

 cesses of the cervical vertebrae in other animals. 



