1882.] SPECIES OF HYPEROODON. 393 



and the foratnen magnum and the condyles are considerably smaller, 

 as seen by the following dimensions : — 



H.pJanifrons. H. rostratus. 



millim. millim. 

 Height of supraoccipital, from upper margin 



of foramen magnum to top of occipital crest 375 340 

 Width of supraoccipital, at narrowest part be- 

 tween hinder margins of temporal fossae . . 3/5 432 



Width of foramen magnum 68 83 



Width of condyles 212 257 



Height of condyle 153 192 



Fis:. 1. 



Upper surface of cranium of Hyperoodon planifrcms. 



In the upper surface (fig. 1) the want of bilateral symmetry 

 in the region of the blowholes is extremely marked. The two 

 characteristic prominences overhanging the anterior apertures to the 

 nares, formed by the posterior ends of the prfemaxillfE, with the nasals 

 flanking their inner and the maxillre their outer surface, are larger 

 and more massive than in Hyperoodon rostratus, especially the right 

 one. The groove between them is narrower. The septum between 



27* 



