U.S. NATIONy\L MUSEUM 



BULLETIN 294, PLATE 2 



Auditory Ossicles, tympanic bulla, and periotic, USNM 23794, Thinocetus arthritus 



1, malleus; 2, incus; 3, stapes; 4, tympanic or ventral view of left periotic; 5, cerebral or internal view of left penotic; 

 6, external view of right tympanic bulla; 7, dorsal view of right tympanic bulla and attached malleus; 8, ventral view of 

 right tympanic bulla. 



