So it is with fishes.
Numerous cases could be given of striking resemblances in quite distinct beings between single parts or organs, which have been adapted for the same functions.
A good instance is afforded by the close resemblance of the jaws of the dog and Tasmanian wolf or Thylacinus--animals which are widely sundered in the natural system.
But this resemblance is confined to general appearance, as in the prominence of the canines, and in the cutting shape of the molar teeth.
For the teeth really differ much: thus the dog has on each side of the upper jaw four pre-molars and only two molars; while the Thylacinus has three pre-molars and four molars.