1 44 ELEMENTAR Y ANA TOM Y. [LESS. 



and mastoidal portions of the temporal bone we have a 

 transitory representation of the permanent conditions of the 

 same parts in the osseous Fishes. 



In the distinct osseous origins of the wings of the sphenoid, 

 of the basi-occipital and basi-sphenoid, and of the lateral 

 parts of the occipital bone, there is exhibited a resemblance 

 to the permanent condition of those parts as they exist in 

 many animals, as has been already noticed. 



FIG. 122. SIDE VIEW OF THE CARTILAGINOUS SKELETON OF THE HEAD OF 

 A SHARK 



This shows the successive arches except the first pair, or trabeculte cranii, which 

 form the base of the skull in front of the pituitary fossa. 



pg, pterygo-palatine, or second arch ; m, mandibular, or third arch ; h, hyoidean, 

 or fourth arch (the corniculum, stylo-hyoid ligament, styloid process, &c , ot 

 man) From behind it the branchiostegal rays are seen extending backwards, 

 6 1 to 65, the branchial arches forming the fifth, sixth, seventh, eighth, and 

 ninth arches of the skull. 



The same remark applies to the other parts which, at first 

 distinct, ultimately coalesce, such as the portions of the 

 ethmoid, the upper maxillary bones, the pterygoid processes, 

 and the squamous element of the temporal bone. 



Finally, that exceptional anchylosis which occasionally 

 takes place in aged skulls recalls to us that union of the 

 cranial elements which in some Vertebrates, as in Birds, is so 

 much more complete than is normally the case with the bones 

 constituting the human cranium. 



The consideration of the relations existing between Meckel's 

 cartilage and the summit of the hyoidean arch in man with 

 the suspensorial and mandibular structures of lower Verte- 

 brates, must be deferred until the internal ear is treated of, 

 and we come to examine the essential nature of its auditory 

 ossicles. 



