22 DINOCEUATA. 



The Squamosal Bones. 



The squamosal forms the hnver jjortion of the temporal foss;i, and 

 sends down a massive post-glenoid process (Plate II, s), which hounds 

 in front the external auditory meatus. The latter has for its jiosterior 

 border the post-tympanic process of the squamosal, whicli unites directly 

 with the par-occipital process by close suture. 



The periotic and tympanic bones are co-ossified, but not with the 

 squamosal. Tlie periotic has a distinct floccular fossa on its inner side. 

 The tympanic is small, and is not expanded into a distinct bulla. 



The squamosal sends forward a strong- zygomatic process, which 

 resembles that in Taplnis. This process overlaps the malar, uniting to 

 it by a straight, horizontal, suture, which, in very old animals, may nearly 

 or quite disappear. 



The Malar Bones. 



The malar bone completes tlie anterior poition of the zygomatic arch, 

 extending to the front of the orbit, as shown in Plate II, m<i. The suture 

 uniting the malar with the maxillary remains distinct till adult life, and 

 may usually be traced, even in old animals. This forward extension of 

 the malar bone is a general ungulate chai'acter, aiul quite different from 

 what is seen in the Proboscidians, where the malar forms the middle 

 portion only of the zygomatic arch. Union of malar with zygomatic 

 process. 



The Lachrymal Bones. 



The lachrvmal is large, and forms the anterior border of the orbit, as 

 shown in Plate II, I. It is perforated by a large foramen. In Dimceras, 

 this opening is well within the orbit. In some species of Tinoceras, it is 

 outside the orbit. The base of the lachrymal is excavated for the posterior 

 opening of the large antorbital foramen. 



