HYRACOIDEA. 



179 



The mandible has a high and exceedingly broad ascending 

 portion, its hinder margin being produced far behind the 

 condyle, but the angle is rounded, and without any distinct 

 process. The condyle is much extended transversely, and 

 narrow from befoi'e backwards, especially in its inner half, 

 for externally it is somewhat rounded. The coronoid pro- 

 cess is small and recurved. 



The hyoid apparatus of the Hyrax is unlike that of any 

 other known Mammal. The basihyal is oval, transversely 

 extended and flat, with a small median eminence on its 

 anterior border, and an emarginate posterior border, only 

 ossified in the centre, and prolonged laterally, without any 

 definite segmentation, into broad, flattened, slightly curved 

 cartilaginous thyrohyals. Articulated to the anterior and 

 external angles of the basihyal are two large, triangular, 

 flattened bones (ceratohyals), each with a long process 

 projecting forwards and meeting in the middle line, so 

 as to enclose (with the anterior margin of the basihyal) a 

 triangular space. There is no other cartilage or bone in the 

 anterior arch, unless a very minute pyramidal bone, described 

 by Brandt as articulating with the mastoid process of the 

 skull, represents the stylohyal.^ 



Order Proboscidea. — The skull of the only existing 

 animals of this order, the Elephants, presents many very 

 remarkable features. As the brain-case increases but little 

 in size during growth, and as the exterior wall of the skull 

 is required to be of great superficial extent to support the 

 trunk and the huge and ponderous incisor teeth or tusks, and 

 to aftbrd space for the attachment of muscles of sufficient 

 size and strength to wield the skull thus heavily weighted, 



^ " Mem. de I'zVcad. Imp, de St.-Petersbourg," VII« Serie, tome xiv. 

 Xo. 2, p. 68. 1869. 



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