Agassiz has described over one hundred and thirty species of Fishes from this locality, belonging to seventy-seven genera.  All the species are extinct; but about one-half of the genera are represented by living forms.  The great majority of the Eocene Fishes belong to the order of the “Bony Fishes” (Teleosteans), so that in the main the forms of Fishes characterising the Eocene are similar to those which predominate in existing seas.  In addition to the above, a few Ganoids and a large number of Placoids are known to occur in the Eocene rocks.  Amongst the latter are found numerous teeth of true Sharks, such as Otodus (fig. 224) and Carcharodon.  The pointed and serrated teeth of the latter sometimes attain a length of over half a foot, indicating that these predaceous fishes attained gigantic dimensions; and it is interesting to note that teeth, in external appearance very similar to those of the early Tertiary genus Carcharodon, have been dredged from great depths during the recent expedition of the Challenger.  There also occur not uncommonly the flattened teeth of Rays (fig. 225), consisting of flat bony pieces placed close together, and forming “a kind of mosaic pavement on both the upper and lower jaws” (Owen).

[Illustration:  Fig. 223.—­Rhombus minimus, a small fossil Turbot from the Eocene Tertiary, Monte Bolca.]

[Illustration:  Fig. 224.—­Tooth of Otodus obliquus.  Eocene.]

[Illustration:  Fig. 225.—­Flattened dental plates of a Ray (Myliobatis Edwardsii).  Eocene.]

In the class of the Reptiles, the disappearance of the characteristic Mesozoic types is as marked a phenomenon as the introduction of new forms.  The Ichthyosaurs, the Plesiosaurs, the Pterosaurs, and the Mosasaurs of the Mesozoic, find no representatives in the Eocene Tertiary; and the same is true of the Deinosaurs, if we except a few remains from the doubtfully-situated “Lignitic formation” of the United States, On the other hand, all the modern orders of Reptiles are known to have existed during the Eocene period.  The Chelonians are represented by true marine Turtles, by “Terrapins” (Emydidoe), and by “Soft Tortoises” (Trionycidoe).  The order of the Snakes and Serpents (Ophidia) makes its appearance here, for the first time under several forms—­all of which, however, are referable to the non-venomous group of the “Constricting Serpents” (Boidoe).  The oldest of these is the Paloeophis toliapicus of the London Clay of Sheppey, first made known to science by the researches of Professor Owen.  The nearly-allied Paloeophis typhoeus of the Eocene beds of Bracklesham appears to have been a Boa-constrictor-like Snake of about twenty feet in length.  Similar Python-like Snakes (Paloeophis, Dinophis, &c.) have been described from the Eocene deposits of the United States.  True Lizards (Lacertilians) are found in some