It could be easily understood by the layman, and its enunciation added vastly to the popular reputation and prestige of the young science of comparative anatomy.[98] In his time, and applied to the forms occurring in the Paris Basin, it was a most valuable, ingenious, and yet obvious method, and even now is the principal rule the palaeontologist follows in identifying fragments of fossils of any class.

But it has its limitations, and it goes without saying that the more complete the fossil skeleton of a vertebrate, or the remains of an arthropod, the more complete will be our conception of the form of the extinct organism.

It may be misleading in the numerous cases of convergence and of generalized forms which now abound in our palaeontological collections.

We can well understand how guarded one must be in working out the restorations of dinosaurs and fossil birds, of the Permian and Triassic theromorphs, and the Tertiary creodonts as compared with existing carnivora.
As the late O.C.Marsh[99] observed: "We know to-day that unknown extinct animals cannot be restored from a single tooth or claw unless they are very similar to forms already known.

Had Cuvier himself applied his methods to many forms from the early tertiary or older formations he would have failed.