

HISTORY OF WHALES 



*75 



undoubtedly traces its origin back to 

 some extinct porpoise in which the outer 

 borders of the maxillaries were turned 

 upward above the orbits. This peculiar 

 structural condition permitted the maxil- 

 laries to grow upward, resulting in the 

 formation of the odd incurved fan-like 



anterior teeth have a high pointed crown 

 and a broad laterally compressed root. 

 The relations of the basicranial bones 

 suggest that the rostrum and braincase 

 have been telescoped to a greater extent 

 and in a somewhat different manner than 

 in other porpoises. To recapitulate the 



Tmx — | 



Max. 



Cr. j 



S. or. pr. ' 



f- Max. 



N*'' 



S. or. 



Fig. iz Fig. 13 



Fig. iz. Dorsal View of Skull 



Zarhachis flagellator, Middle Miocene, Maryland 



Fig. 13. Dorsal View of Skull 



Platanista gangetica, India. Left maxillary crest removed to expose upper surface of cranium 



maxillary structures seen in the living 

 Susu, which cover the facial depression 

 like a mask. The rostrum is so slender 

 and the palate so narrowed that the upper 

 tooth rows lie side by side, and in old 

 individuals apparently merge together at 

 the posterior end of the series. The 



evidence supporting this observation it 

 may be pointed out that in correlation 

 with the depression of the rostrum below 

 the level of the braincase, the narial 

 passages have moved backward and are 

 situated on a level with the anterior 

 margins of the squamosals, the pterygoids 



