728 THE SPERM WHALES, GIANT AND PYGMY. 
a triangular or retrorsely falciform wedge between the max- 
illaries and supraoccipital. The left nasal bone (n) is atro- 
phied; the right hypertrophied and twisted to the left side. 
The: jugal (7) is well developed and projects downwards 
or backwards. The orbit is small or of moderate size. 
The pterygoid (pt) bones are thick, produced forwards and 
entering largely into the bony roof of the mouth over and 
behind the palatine (pal) bones, not contiguous at the mid- 
dle, with low ridges on the oral surface diverging more or 
less backwards and outwards, and with sides not involuted 
so as to form the outer wall of the postpalatine air-sinus. 
The lower jaw has a more or less elongated symphysis. 
Teeth are functionally developed only or chiefly in the lower 
jaw. The pectoral limb is small. 
3. Deductions. Such are the characters possessed by all 
the members of the family. It will be observed that all but 
(Fig. 161.) 
Lower Jaw of Physeter macrocephalus, from Flower. 
one of them which are truly distinctive are derived from the 
internal organization, and as some persons may complain of 
this and ask why external characters have not been em- 
ployed, it may be added that there are no distinctive ex- 
ternal features, except the inferiority of the mouth, and that 
only owes its importance to its coórdination with others. 
It cannot be too often repeated that our judgment respecting 
the relations of animals is only reliable when based on the 
most complete and comprehensive examination of the entire 
Structure, external as well as internal, and that one of the 
first elements of a natural classification is that the characters 
used shall be at least expressive of the sum of all the com- 
mon characters. 
