290 



DAVIDSON BLACK 



ridges (several of which mark the caudo-lateral area of the tuber- 

 culum) and they are beUeved to correspond to skull grooves for 

 the lodgement of strands of the tractus bulbo-tuberculare. 



The optic foramina as evidenced by the cast are approached 

 by way of an elongated channel somewhat depressed and dumb- 



S. I«t. 



S.ss 



R.d.s 



, Pa. ect 



R.I.S5. 



S.cor. 



For: con. ^ob- pet 



Sin.i.lat.r '^For.lac.ant. 



For. ov. n.mfn.m. 



?a. ecf 



?• lat. 



S.cor 

 Tcig. S. \ 



For. lac. ant.--' 



For. ov. 



'M.a.i. 



16 



Figs. 15, 16, 17 and 18 Camera liicida drawings of natural endocranial cast of 

 Oreodon, Specimen IV, right lateral, left lateral, ventral and dorsal views 

 respectively. For photographs see figures 41 to 44. Abbreviations: A. wen. ?«ed., 

 ridges corresponding to branches of the middle meningeal artery; B.o., bulbus 

 olfactorius; R.l.ss., ramus lateralis suprasylvii; R.s.p., ramus posterior supra- 

 sylvii. Other abbreviations as before. 



bell-shaped in cross section. This channel which lodged both 

 optic nerves begins above the shallow pituitary fossa by a single 

 rather wide median aperture and terminates rostrally by bifur- 

 cation. These parts thus present in a somewhat more pro- 

 nounced manner the condition which obtains in this region in 

 Sus and Ovis. 



