abundance in the Eocene deposits,—­some being small terrestrial forms, like the common European lizards of the present day; whilst others equal or exceed the living Monitors in size.  Lastly, the modern order of the Crocodilia is largely represented in Eocene times, by species belonging to all the existing genera, together with others referable to extinct types.  As pointed out by Owen, it is an interesting fact that in the Eocene rocks of the south-west of England, there occur fossil remains of all the three living types of Crocodilians—­namely, the Gavials, the true Crocodiles, and the Alligators (fig. 226)—­though at the present day these forms are all geographically restricted in their range, and are never associated together.

[Illustration:  Fig. 226.—­Upper jaw of Alligator.  Eocene Tertiary, Isle of Wight.]

Almost all the existing orders of Birds, if not all, are represented in the Eocene deposits by remains often very closely allied to existing types.  Thus, amongst the Swimming Birds (Natatores) we find examples of forms allied to the living Pelicans and Mergansers; amongst the Waders (Grallatores) we have birds resembling the Ibis (the Numenius gypsorum of the Paris basin); amongst the Running Birds (Cursores) we meet with the great Gastornis Parisiensis, which equalled the African Ostrich in height, and the still more gigantic Dasornis Londinensis; remains of a Partridge represent the Scratching Birds (Rasores); the American Eocene has yielded the bones of one of the Climbing Birds (Scansores), apparently referable to the Woodpeckers; the Protornis Glarisiensis of the Eocene Schists of Glaris is the oldest known example of the Perching Birds (Insessores); and the Birds of Prey (Raptores) are represented by Vultures, Owls, and Hawks.  The toothed Birds of the Upper Cretaceous are no longer known to exist; but Professor Owen has recently described from the London Clay the skull of a very remarkable Bird, in which there is, at any rate, an approximation to the structure of Ichthyornis and Hesperornis.  The bird in question has been named the Odontopteryx totiapicus, its generic title being derived from the very remarkable characters of its jaws.  In this singular form (fig. 227) the margins of both jaws are furnished with tooth-like denticulations, which differ from true teeth in being actually portions of the bony substance of the jaw itself, with which they are continuous, and which were probably encased by extensions of the horny sheath of the bill.  These tooth-like processes are of two sizes, the larger ones being comparable to canines; and they are all directed forwards, and have a triangular or compressed conical form.  From a careful consideration of all the discovered remains of this bird, Professor Owen concludes that “Odontopteryx was a warm-blooded feathered biped, with wings; and further,