200 



VERTEBRATE SKELETON 



which bears the condyle and in front of this is a more or less promi- 

 nent coronoid process on which the temporalis muscle is inserted. 

 When the animal does little chewing (Monotremes, anteaters, mana- 

 tees, whales, etc.) the process is very small. In many lower 

 mammals the dentale is extended backwards at an angle where ramus 

 and body meet, this angle being inflected in Marsupials and some 

 Insectivores, while in many rodents the strain of the pterygoid muscle 

 has developed a shelf on the inner side near the angle. 



In reality several bones of. the lower jaw of the non-mammals may be traced 

 in the mammals. The true dentale forms in front, mostly on the outer and 

 inferior sides of the Meckelian, a splenial forming medial to and just above the 

 cartilage, this forming part of the alveolar border. Some mammals have a large 

 cartilage lateral to the Meckelian at the angle of the jaw, which has been doubt- 

 fully compared to the lower labial of fishes. On the upper margin of this carti- 

 lage is a distinct dermal ossification to which the temporal muscle is attached, 

 thus corresponding in position and muscular relations to the coronoid bone of 

 lower forms. The angularc has already been mentioned in connexion with the 

 tympanic bone; the goniale will be considered in connexion with the malleus 

 (p. 202). 



The hyoid apparatus is largely ossified, both hyoid and first 

 branchial arches participating (fig. 207), while there is a ligamentary 

 connexion with the second branchial arch, the 

 thyreoid cartilage of the larynx. The hyoid 

 body (basihyal or basibranchial i ?) is occa- / A 



sionally plate-like but is usually a transverse 

 bar and is sometimes continued forwards as 



Fig. 207. — Cartilage hyoid apparatus of 27 mm. dog 

 embryo (Olmstead, '11). a. arytenoid; b, ist branchial; 

 c, hyoid body; h, hyoid arch; p, parotic crest; t, thyreoid 

 cartilage. 



Fu;. 208. — Hyoid of 

 howling monkey. Myceles 

 (Pouchet et Beauregard, 

 '89). 



a short entoglossal (glossohyal) process. In the howling monkeys 

 {Myceles, fig. 208) it is expanded and excavate, forming a 

 resonator for the voice. To the body are attached two pairs of 

 cornua (visceral arches), the hyoid of man being the lesser cornu, 

 the branchial the greater, but in most mammals the hyoid cornu is 



