so8 



CLASS MAMMALIA. 



probably nearly related to the existing Steno. Delphinoid remains 

 from the Miocene of North America have been described by Pro- 

 fessors Leidy and Cope under the names of Priscodeifihinus, Tetro- 

 sfihys, Zarhachis, Lofihocetus, Rhabdosteus, Ixacanthus, Anoplonassa, 



Fig. 1 1 80. — Skeleton of the Manatee {Manatus australis). Greatly reduced. 



and Orycterocetus ; but further information is required as to the 

 affinity of these forms and their right to generic distinction. 



Order V. Sirenia. — The Sirenia, now represented only by the 

 Manatees and Dugongs, agree with the Cetacea in their adaptation 

 for a purely aquatic life, and accordingly present a strong general 

 resemblance in their external contour to the members of that order. 

 The head is, however, of normal relative size ; the tail has a hori- 



Fig. 1181. — Dorsal view of the right pectoral limb of Manatus australis. Much reduced. 

 s, Scapula ; h, Humerus ; r, Radius ; u, Ulna ; J>, Pollex. 



zontal membranous expansion ; the pectoral limbs, although modified 

 into paddles (fig. 1 1 8 1 ), retain the normal number of phalangeals ; 

 all external traces of the pelvic limbs are wanting ; and the surface 

 of the body is either naked or covered with sparse bristles. The 

 lips are fleshy ; the nostrils placed near the extremity of the muzzle 



