Sub-Order ODONTOCETI— TOOTHED WHALES 
Family PHYSETERID^. 
Genus Physeter. 
THE SPERM WHALE OR CACHALOT. 
Physeter macrocephalus, Linnaeus. 
Plate 4.J. 
The various members of this group (Odontocett) are distinguished by 
the possession of teeth, which may be numerous in both upper and 
lower jaws, or confined to a single pair in the latter ; there is also no 
whalebone. The nostrils are united below the surface and form one 
external blowhole. The skull is not symmetrical. 
The Sperm, by far the largest of these toothed whales, measures up 
to and over 60 feet, the females being considerably less. The huge head, 
appearing as if cut off abruptly in front, and taking up about one third 
of the whole length of the body, is curiously shaped, the massive upper 
part being adapted as a sort of well or receptacle to contain the valuable 
oily fluid known as spermaceti. The blowhole is placed very far for- 
ward on the left-hand side and near the extremity of the head. The 
first vertebra of the neck is free, the others united. 
The upper jaw reaches considerably beyond the lower. 
One or more rounded protuberances on the back represent the dorsal fin. 
The flippers are broad and unpointed. In the lower jaw are from 
twenty to twenty-five pairs of hooked teeth, those in the upper jaw 
being rudimentary and buried in the gum. 
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