Lect. VI.] LABYRINTH OF THE EAR. 155 



cavity ; these are in the hard lumj) of bone behind our 

 outer ear. 



The parts of the hind skull, especially, are well ancliy- 

 losed or melted into a common mass, as in Birds and 

 Bats, not, however, for the same teleological reason, 

 manifestly. 



The whole skull is a wedge, and the nose a borer, fas- 

 tened to the sharp end of the wedge. 



One thing surprises the student of the high forms of 

 mammals, namely, that in front of the petrous bone (or 

 stony ear capsule) in the Mole, there are two temporal 

 scale-bones, apparently. The one in front of and below 

 the other is the true superficial squamosal, or squama 

 temporis ; the one behind and above is a large semi-oval 

 tract of the original cartilaginous skuU wall, ossified by 

 the prootic bone (petrosum). The temporo-mastoid bone 

 (opisthotic), which in us forms the lump just spoken of, 

 ossifies the cochlea (or snaU-sheU), the mastoid region, 

 and most of the walls of the capsule where the semi- 

 circular canals, most elegant parts of the labyrinth, are 

 embedded. The occipital arch, or back of the head, 

 is very large and swelling, and the condyles or hinges 

 for the first neck-joint are large also ; the jugal arch 

 (cheek) is perfect, but very delicate. 



The hyoid arch — the second, or that which carries 

 the tongue — is complete, but it is swung, as in Mammals 

 generally, and also in Frogs and Toads (which curiously 

 anticipate many things in mammalian morphology), from 



