Thus to explain practically all the deposits found in the rocks, we are absolutely limited to the shore deposits and the mouths of large rivers. Here we certainly have alternations of sand, clay and gravel, producing a true bedded structure. But I ask: What kind of organic remains will we get from these modern deposits? Certainly nothing like the crowded graveyards which we find everywhere in the ancient ones. Darwin, in his famous chapter on "The Imperfection of the Geological Record," has well shown how scanty and imperfect are the modern fossiliferous deposits. The progress of research has only confirmed and accentuated the argument there presented on this point. Thus Nordenskiold, the veteran Arctic explorer, remarks with amazement on the scarcity of recent organic remains in the Arctic regions, where such a profusion of animal life exists; while in spite of the great numbers of cats, dogs and other domestic animals which are constantly being thrown into rivers like the Hudson or the Thames, dredgings about their mouths have revealed the surprising fact that scarcely a trace of any of them is there to be found.[56] Even the fishes themselves stand a very poor chance of being buried intact. As Dana[57] puts it: "Vertebrate animals, as fishes, reptiles, etc., which fall to pieces when the animal portion is removed, =require speedy burial after death=, to escape destruction from this source (decomposition and chemical solution from air, rain-water, etc.), as well as from animals that would prey upon them." If a vertebrate fish should die a natural death, which of itself must be a rare occurrence, the carcass would soon be devoured whole or bit by bit by other creatures near by. Possibly the lower jaw, or the teeth, spines, etc., in the case of sharks, or a bone or two of the skeleton, might be buried unbroken, but a whole vertebrate fish entombed in a modern deposit is surely a unique occurrence.