The objection that broad statements of this kind, after all, rest largely on negative evidence is obvious, but it has less force than may at first be supposed; for, as might be expected from the circumstances of the case, we possess more abundant positive evidence regarding Fishes and marine Mollusks than respecting any other forms of animal life; and yet these offer us, through the whole range of geological time, no species ordinarily distinct from those now living; while the far less numerous class of Echinoderms presents three, and the Crustacea two, such orders, though none of these come down later than the Palaeozoic age. Lastly, the Reptilia present the extraordinary and exceptional phaenomenon of as many extinct as existing orders, if not more; the four mentioned maintaining their existence from the Lias to the Chalk inclusive. Some years ago one of your Secretaries pointed out another kind of positive palaeontological evidence tending towards the same conclusion--afforded by the existence of what he termed "persistent types" of vegetable and of animal life.[36] He stated, on the authority of Dr. Hooker, that there are Carboniferous plants which appear to be generically identical with some now living; that the cone of the Oolitic _Araucaria_ is hardly distinguishable from that of an existing species; that a true _Pinus_ appears in the Purbecks and a _Juglans_ in the Chalk; while, from the Bagshot Sands, a _Banksia_, the wood of which is not distinguishable from that of species now living in Australia, had been obtained. Turning to the animal kingdom, he affirmed the tabulate corals of the Silurian rocks to be wonderfully like those which now exist; while even the families of the Aporosa were all represented in the older Mesozoic rocks. Among the Mollusca similar facts were adduced. Let it be borne in mind that _Avicula_, _Mytilus_, _Chiton_, _Natica_, _Patella_, _Trochus_, _Discina_, _Orbicula_, _Lingula_, _Rhynchonella_, and _Nautilus_, all of which are existing _genera_, are given without a doubt as Silurian in the last edition of "Siluria;" while the highest forms of the highest Cephalopods are represented in the Lias by a genus, _Belemnoteuthis_, which presents the closest relation to the existing _Loligo_. The two highest groups of the Annulosa, the Insecta and the Arachnida, are represented in the Coal, either by existing genera, or by forms differing from existing genera in quite minor peculiarities. Turning to the Vertebrata, the only palaeozoic Elasmobranch Fish of which we have any complete knowledge is the Devonian and Carboniferous _Pleuracanthus_, which differs no more from existing Sharks than these do from one another.