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the bony palate. The Toxodon further differs from the Manatee and 

 Dugong in the firm nature of the connexion of the bones of the head ; 

 and it differs from the Hippopotamus in the strong attachment of the 

 intermaxillary bones to the maxillaries. 



The anterior part of the zygoma is formed externally by the malar 

 bone, which in its position is intermediate to the Rodent and Pachyder- 

 matous structures. It is not suspended in the middle of the zygomatic 

 arch, as in the former order, neither does it extend into the region of 

 the face so far anterior to the orbit as in the Tapir or Hippopotamus. 

 The exterior line of the malo-maxillary suture defines the orbit anteriorly ; 

 but from this line the maxillary bone extends backwards, along the inner 

 side of the malar portion of the zygoma, until it almost reaches the tem- 

 poro-malar suture ; thus abutting by an oblique surface against nearly 

 the whole internal facet of the malar bone, and materially contributing 

 to the general strength of the zygomatic arch. The malar bone is of 

 considerable vertical extent, and presents a rugged and thickened inferior 

 margin for the attachment of the masseter. The upper margin of the 

 malar bone is smoothly rounded, and presents a regular semicircular 

 excavation, forming the lower boundary of the orbit. The relative mag- 

 nitude of the zygomata to the entire cranium far exceeds in the Toxodon 

 that which exists in the Hippopotamus or any other known Pachyderm. 

 This arises from the great vertical development of the malar bone behind 

 the orbit, and the vertical expansion of the temporal portion of the arch. 

 The oblique position of the zygoma, descending as it advances forwards, 

 is deserving of attention, as the Toxodon, in deviating from the Pachy- 

 derms in these respects, makes an evident approach to the herbivorous 

 Cetaceans, as the Dugong and Manatee : in the latter Cetacean we observe 

 a similar development of the lower part of the zygomatic process of the 

 malar bone. It is here, also, that we may perceive an indication of a 

 resemblance between the Megatherium and Toxodon. 



There is no discernible trace of the lachrymal bone having extended, 

 as in the Hippopotamus, beyond the anterior boundary of the orbit : the 

 lachrymal foramen is situated rather deeply in the orbit, and the bone 

 itself appears to have been of very small size. 



