Plate LI 



Comparative Series: Xorina Basalis of tlie Skull of Tarftiux, Tcfoinus-, and N crrolcvuir 



Tarsius spectrum. Ainer. Mus. No. 64. The prominent foramen for the internal carotid artery is shown perforating the middle 

 of the inferior surface of the greatly expanded bulla. On the left side the lower part of the bulla has been removed and the cochlea is 

 shown in section. At the apex of the cochlea is a section of the carotid canal. (The lumen of this canal does not show in the plate.) 

 The bristle indicates the imsition of the cavum tympani and Eustachean foramen. Three times natural size. 



Tetonius (" Aim jiln/iior /ih us" ) lioui unciil ks (Cope). Amer. Mus. No. 4194. Lower Eocene, Gray Bull beds, Bighorn Basin, Wyo- 

 ming. On the left side is shown the audit ory prominence, or cochlea, which is much smaller than that of Tarsius. Adhering to the 

 cochlea is the remnant of the septum bull» and possibly of the carotid canal. In front of the cochlea is the cavum tympani. The bullse 

 were evidently greatly expanded and extended anterointernally toward the midline, pressing against the alisphenoid laterally and against 

 the basisphenoid anteriorly. Three times natural size. 



Necrolernur antiquus. Peabody Mus. Comp. Zool., Harvard Univ. The greatly inflated bullse extend far forward and inward and 

 are overlapped by the alisphenoid. The carotid foramen is on the medial wall of the bulla near its junction with the basioccipital and 

 just in front of the slit-like foramen lacerum posterius. Four times natural size. 



