THE SKELETAL SYSTEM 



175 



into a broad lamina on its dorsal or posterior surface. Articulating with 

 the cricoid on its dorsal cranial edge is a pair of pyramid-shaped arytenoid 

 cartilages, so-called because of their resemblance in section to a funnel. 

 A fifth cartilage supports the epiglottis. The cartilages which support the 

 trachea may also doubtfully belong to the visceral skeleton. They form a 

 series of incomplete rings extending along the trachea. 



QUADRATE 

 I 



PAU\TO-PTERYGOID 



ARTICULAR- -... 



DENTARY 



^ HYOMANDIBULAR 



.HYOID 



MANDIBULAR 



B TELEOST 



STYLOID PROCESS 



lYoiDj r 



STAPES CHYOMANDI8ULAR> 



INCUSCQUADRATEJ— 



MALLEUS CARTICULAR) 



MECKEL'S 



CARTILAGE CMANDIBULAR)^ 



HYOID 



DENTARY- 

 STYLOHYOID LIGAMENT CHYOID) - 



MANDIBULAR 



A ELASMOBRANCH 



HYOMANDIBULAR (COLUMELLA) 



QUADRATE 



ARTICULAR 



DENTARX. 

 MANDIBULAR - 



C AMPHIBIAN AND REPTILil. D. MAMMAL. 



Fig. 164. — Diagrams of the first and second visceral arches in A, Elasmobranch; B, 

 Teleost; C, Amphibian and Reptile; and D, Mammal, illustrating the transformation 

 of the hinge of the jaw of lower vertebrates into the malleus and incus of the mammal. 

 The third earbone, the stapes, comes from the hyomandibular. (Redrawn after 

 Gegenbaur and Stempell.) 



The three ear bones are named malleus, incus, and stapes from their 

 fancied resemblance to hammer, anvil, and stirrup. Within the cavity 

 of the middle ear they extend in the order given from the ear drum or 

 tympanum to the oval window or fenestra vestibuli of the internal ear. 

 Thus they serve to carry vibrations from the ear drum to the liquids of 

 the internal ear. See Fig. 369. 



