THE SKULL. 



31 



In the type of Binnceras, the palatine fossa of the posterior nares is 

 roofed over, so that tlie passage from the palate into the large nasal 

 cavities above leads for\yard and upward, as shown indistinct] v in figure 

 26, e, page 26. In Tinoeeras ingens and Tinoceras iniijnax, the i-oof of this 

 fossa is excavated in front by a pair of oval apertures, and through 

 these the postei-ior nares open directly up\yard, as represented in figures 

 28 and 29, e, on page 27. The existing perissodactyls, the liorse, the 

 tapir, and rhinoceros, have the same type of palate. In l^'ii/fntJ/eriiDii, the 

 structure of this portion of the skull has not yet been determined with 

 certainty. 



( 



Figure 34. — Vertical mediau longitudinal section of sl^uU oC Dinoceras mirabile. Marsli. 



Figure 35. —Vertical transverse section of sliull of Dinuceras mirahik. 



b. brain-cavity ; c. cavities in cranial walls ; /. frontal bone ; m. maxillary bone ; m'. maxillary protuber- 

 ance ; n. nasal bone ; »'. naaal protuberance ; o. occipital condyle ; ol. olfactory lobes of br„iu ; op. optic 

 foramen; p. parietal bone; ;/. parietal protuberance; pg. post-glenoid process; pi. palaiine bune ; 

 pm. premax llary bone ; pt. pterygoid bone ; s. supra-occipital crest ; z. zygomatic process of squamosal. 



Both figures are one-eighth natural size. 



These })alatine characters of the Dinocerafa are important, but 

 unfortunately they can be made out only in skulls unusualh' well 

 preserved. The value of these characters in classification Mill, be 

 discussed in a subsequent chapter 



