THE SKELETON IN MAMMALIA. AUDITORY OSSICLES. 485 



remarkable for the large expanded basi-hyal, which is generally 

 concave above and convex below. The anterior cornu is never 

 well ossified, but the thyro-hyal is always strong. In Mycetes 

 the basi-hyal is enormously large, forming a somewhat globular 

 thin-walled capsule. 



AUDITORY OSSICLES. 



There are in mammals four auditory ossicles forming a 

 chain extending from the fenestra ovalis to the tympanic 

 membrane. Three of these, the malleus, incus and stapes, 

 are always distinct, while the fourth, the lenticular, is smaller 



FIG. 100. MALLEUS, STAPES AND INCUS OF 

 A. MAN. B. DOG. C. RABBIT. (After DOBAN) x 1. 



1. head of malleus. 5. manubrium of malleus. 



2. canal of stapes. 6. processus brevis. 



3. incus. 7. lamella. 



4. processus longus (or gracilis). 



than the others and is sometimes not distinct. The names are 

 derived from human anatomy and indicate in the case of the 

 first three a more or less fanciful resemblance respectively to a 

 hammer, an anvil, and a stirrup. The ossicles are homologous 



