MIOCENE PORPOISES — KELLOGG 119 



Greatest dorsoventral depth of peri- 

 otic (as measured from most in- 

 flated portion of tympanic face of 

 pars cochlearis and groove to most 

 projecting point on cerebral face) 15. 4 13. 1 12. 



Distance between fenestra rotunda 



and tip of anterior process 21. 20. 17. 3 



Distance between fenestra rotunda 

 and anteroexternal angle of poste- 

 rior process 15. 2 13. 5 15. 6 



Distance between epitympanic ori- 

 fice of aquaeductus Fallopii and tip 

 of anterior process 16. 6 16. 14. 



TYMPANIC BULLA 



The right tympanic bulla (pi. 6, figs. 4, 5) lacks the posterior 

 process and most of the thin outer lip, including the uncinate process. 

 The sigmoid process is preserved, but the intervening portion of the 

 outer lip is missing and consequently its position cannot be determined 

 with accuracy. 



The ventral and external surfaces of this tympanic bulla are some- 

 what roughened but are not as nodular as the ventral face of the bulla 

 of Inia geqffrensis. The configuration of the involucrum, however, is 

 quite unlike that of Inia geqffrensis, and is somewhat similar to that 

 of Lipotes vexillifer. 



The anterior end of the tympanic bulla is flattened, forming a 

 narrow lip which projects forward, and the thin outer lip is suffi- 

 ciently complete to indicate the size and direction of the anterior 

 outlet of the eustachian canal. The involuted thicker portion of the 

 tympanic bulla is depressed below the level of the arching thin outer 

 Up and is abruptly attentuated about 10 mm. behind the anterior 

 outlet of the Eustachian canal. The surface of the involucrum is 

 slightly roughened, convex from side to side, and depressed opposite 

 the sigmoid process. 



The ventral surface of the tympanic bulla is somewhat flattened on 

 the anterior 15 mm. of its length. A large deep groove behind this 

 flattened area divides the ventral surface longitudinally. 



Measurements of Right Tympanic Bulla of USNM 15985 (in millimeters) 

 Greatest length of bulla 38. 



Greatest depth of bulla on internal side (ventral face to dorsal 



face of involucrum) 14. 



Greatest width of involucrum 11. 1 



TEETH 



During the removal of the matrix, 75 detached teeth were foimd 

 near the skull and mandibles. The detached teeth range from 19.8 to 



