1882. ] SPECIES OF HYPEROODON. 393 
and the foramen magnum and the condyles are considerably smaller, 
as seen by the following dimensions :— 
H.planifrons. 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 fosse .. 375 432 
Width of foramen magnum ........... attenies 83 
Width of condyles ............. areas AMOI, 257 
Height of condyle ......... ct iat ee waSi Fi 192 
Upper surface of cranium of Hyperoodon planifrons. 
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 praemaxillz, with the nasals 
flanking their inner and the maxilla 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* 
