8 PROCEEDINGS OF THE NATIONAL MUSEUM vol. G6 



mm. 



Greatest antei'o-posterior diameter of enamel crown of third tooth at 



base, right mandible 32 



Eighth tooth, right mandible: 



Transverse diameter of tooth at level superior face mandible 82 



Transverse diameter of dentinal axis 50 



Greatest width of cement in same place 1& 



Pulp cavity closed. ^ 



Eighth tooth, left mandible: 



Transverse diameter of tooth at level superior face of mandible 93 



Transverse diameter of dentinal axis 62 



Greatest width of cement in same plane 19 



Pulp cavity closed. 



Ninth tooth, right mandible: 



Transverse diameter of tooth at level of superior face of mandible 80 



Transverse diameter of dentinal axis 46. 3 



Greatest width of cement in same plane 19 



Transverse diameter of pulp cavity at same plane 7. 5 



EXPLANATION OF PLATES 



Plate 1 



Dorsal view of type rostrum and mandibles of Ontocetus oxymycterus 

 The internal face of the left mandible is covered with the matrix. 

 Abbreviations: Max, maxilla; Pmx. premaxilla. 



Plate 2 



Lateral view of type rostrum and dorsal view of right mandible of Ontocetus 



oxymycterus 



This view shows that the extremity of rostrum is formed by the premaxillae; 

 the end of the maxilla, which normally forms the external wall of the fourth 

 alveolus, is missing. 



Abbreviations : Max. maxilla ; Pmx. premaxilla. 



o 



