ZEUGLODON 345 



skull is very long and narrow ; the nostril single, with an 

 upward aspect, above and near the orbits. The jaws are armed 

 with teeth of two kinds, set wide apart ; the anterior teeth 

 have subcompressed, conical, slightly-recurved, sharp-pointed 

 crowns, and are implanted by a single root ; the posterior teeth 

 are larger, with more compressed and longitudinally extended 

 crowns (fig. 108), conical, but with a more obtuse point, and 

 with both front and hind borders strongly notched or serrated. 

 The crown is contracted from side to side in the middle of 

 its base, so as to give its transverse section an hour-glass form 

 (fig. 109), and the opposite wide longitudinal grooves which 

 produce this form 

 become deeper 



as the crown 



-.■ ■ .■.•"' 

 approaches tin.' jHSHw 



socket, where y /ffi^^'l 



they meet and 



divide the root 



into two fangs. s 109 ' 



rrn n 7 Transverse section of a tooth of the Zeuglodon. Nat. size. 



j. ne name Zieu— 



glodon (yoke-tooth) refers to this structure. The mode of suc- 

 cession of the teeth in this genus conforms to the general 

 mammalian type more than does that of any of the existing 

 carnivorous Cetaceans. In the figure given by Dr. Cams* of a 

 portion of the jaw of Zeitglodon ceto'ides, a deciduous molar (fig. 

 108, a) is about to be displaced and succeeded, vertically, by 

 a second larger molar. This mode of succession is not known 

 in the Platanista or Inia, which among existing true Cetacea 

 present teeth most like those of Zeuglodon ; but it is a mode 

 of succession and displacement affecting certain teeth in the 

 herbivorous Cetacea, or Sirenia; and we thus seem to have in 

 the Zeuglodon another of those numerous instances of a more 

 generalized character of organization in older tertiary Mam- 



* Nova Acta Cses. Leop. Carol., vol. xxii., tab. xxxix. B, fig. 2, p. 340. 



