in.] THE CRANIAL SKELETON. 113 



The lower turbinals may be noticed next after the ethmoid, 

 being of cognate nature. 



The simplicity of their structure in man would hardly lead 

 us to anticipate the size and complexity which they may 

 attain in some animals, e.g. in the Badger and the Sheep'. 

 They may, on the contrary, abort altogether, as is the case 

 in the probably smell-less Porpoises. In the Elephant they 

 are but rudimentary. 



In Fishes these bones are quite absent, and in Batrachians 

 are represented by a mere cartilaginous rudiment. 



In Reptiles they are simple, and quite, or almost entirely, 

 cartilaginous, though with a slight bony outgrowth in the 

 Crocodile. But in Birds they may be represented by two or 

 three insignificant ossifications. 



25. As to the MAXILLARY bone, we will consider first the 

 whole of it except that small portion in which the incisor 

 teeth are implanted ; such whole being the bone called " the 

 maxillary bone/' or "maxilla," in other vertebrate animals 

 generally. 



In that it presents an external facial part, an internal 

 nasal part, an inferior palatine part, and a superior orbital 

 part, the maxillary bone of man agrees with that of almost 

 all Mammals. 



In lower forms, except the Crocodilia, the maxilla is much 

 smaller, and it may be a mere filiform rudiment, as in Silu- 

 roids, or abort altogether, as in the Siren and the Myxinoids. 



It may, on the contrary, be represented by several dis- 

 tinct and separate bones placed in a series along the jaw, as 

 is the case in the bony Pike (Lepidosteus). 



Very often its length may greatly exceed its height, as in 

 the Great Ant-eater and in Cetaceans. 



In that the bone bears teeth, we have in man a character 

 which is by no means universal in his class, as e.g. in the 

 Ant-eaters, Whalebone Whales, and the Echidna, the maxilla, 

 like every other bone of the skull, is edentulous. The same 

 is the case in Birds and Tortoises, but in many Fishes (as e.g. 

 the Cod) the maxilla may be edentulous, while nevertheless 

 other bones of the face bear teeth. 



The facial surface of the bone is occasionally much swollen 

 out, as in the Baboons. Sometimes, as in the Paca, this 

 surface is rough and pitted, while the bone is excavated by 

 a large fossa which opens on the inner surface. Again, the 

 facial surface may be very imperfectly ossified and may pre- 

 sent a reticulated structure, as in the Hares. 



I 



