CETACEA, 



587 



The Two Sub-Orders of living Cetaceans may be contrasted 

 as follows (after Flower) : — 



Mystacoceti or Bal^noidea, 

 baleen Cetaceans. 



Odontoceti or Delphinoidea, 

 toothed Cetaceans. 



The teeth are absorbed before birth. 



Whale-bone or baleen-plateS develop as 

 processes from the palate. 



The skull is symmetrical. 



The nasals roof the anteriornasal passages, 

 which are directed upwards and for- 

 wards. 



The maxilla does not overlap the orbital 

 process of the frontal. 



The lachrymal is small and distinct from 

 the jugal. 



The tympanic is ankylosed to the periotic. 



The rami of the mandible are arched out- 

 wards and have no true symphysis. 



All the ribs articulate only with the trans- 

 verse processes of the vertebree. 



The sternum is a single piece, and articu- 

 lates with a single pair of ribs. 



The external nostrils are separate. 



The olfactory organ is distinctly de- 

 veloped. 



There is a short caecum. 



Examples : — 



The right-whale {Bal^na), the 

 hump-back {Megapterd), the 

 rorqual {Balcenopterd). 



The teeth persist after birth, and are 

 generally numerous and functional. 



There is no baleen. 



The skull on its upper surface is more or 

 less asymmetrical. 



The nasals, often small, do not roof the 

 anterior nasal passages, which are di- 

 rected upwards and backwards. 



The maxilla covers most &f the orbital 

 process of the frontal. 



The lachrymal iS fused to the jugal, or is 

 large and helps to roof the orbit. 



The tympanic is not ankylosed to the 

 periotic. 



The rami of the mandible are straight and 

 form a symphisis. 



Several anterior ribs articulate by capi- 

 tula with the centra of vertebra;. 



The sternum has usually several segments 

 with which several sternal ribs articu- 

 late. 



The nostrils unite in a single blow-hole on 

 the top of the head. 



The olfactory organ is rudimentary or 

 absent. 



There is no CEecum, except in Platanista. 



Examples: — 



The Sperm-whale {Physeter)^ the 

 dolphin {Delphinus), the porpoise 

 {P hoc^na) ft\iQ 'Grampus' {Orca), 

 the Ca'ing Whale {Globicephaliis), 

 Grampus^ the Narwhal {^ono- 

 doTi) with a horn-like tusk in the 

 male only, the Beluga {Delphin- 

 apterns), the blind Platanista of 

 the Ganges. 



