PHOCJENA CRASSIDENS. 517 



to its length, especially across the maxillary portion : it 

 has shorter temporal fossae and more numerous teeth. The 

 general resemblance of the fossil to the skulls of the 

 Grampus and Round-headed Porpoise is much closer, and 

 its distinctive character requires more detailed comparison 

 with these for its demonstration. The following are di- 

 mensions of the cranium of the fossil and of the closely 

 allied recent species : 



Crassidens* Orca. Melas. 

 In. In. In. 



1. Length of the skull from the back part of the condyles 



to the end of the beak . . . .26 36 24 



2. Length of the beak from the front end of the malar 



bones ...... 12 17 13 



3. Breadth of the skull across the post-orbital processes of 



the frontal bones .... 15 21 15J 



4. Height of the skull from the lower part of the condyles 



to the top of the occipital crest . . . 9J 1 5 9 



5. Breadth of the beak across its middle part . 7 1 6 J 



6. Length of the alveolar series, lower jaw, . 94 15 6JJ 



7. Length of the lower jaw . . . 20 29 19 



These dimensions show the close agreement between 

 the fossil and the skull of the Phoctena melas in general 

 size, but the sixth admeasurement demonstrates an im- 

 portant difference in the extent of the dental series : and 

 this difference does not depend on a corresponding differ- 

 ence in the number of the teeth, which might have been 

 merely the effect of age ; for the lower jaw of the Ph. 

 melas, the subject of comparison, has eleven teeth in the 

 alveolar series of each ramus, whilst the fossil jaw has 

 only ten. The greater extent of the dental series in this 

 jaw depends on the considerably larger size of the teeth 

 in the fossil, as the following dimensions show : 



Crassidens. Orca- Melas. 



In. In. In. 



Circumference of the base of the crown of the largest tooth 241 

 Length of the crown of do. . . . . 12 J f 



