[Illustration: FIG. 25.--THE "SEA SERPENT," ON THE ENALIOSAURIAN HYPOTHESIS. _After_ Mr. P. H. GOSSE, F.R.S.] Professor Agassiz, too, is adduced by a correspondent of the _Zoologist_ (p. 2395), as having said concerning the present existence of the _Enaliosaurian_ type that "it would be in precise conformity with analogy that such an animal should exist in the American Seas, as he had found numerous instances in which the fossil forms of the Old World were represented by living types in the New." On this point, Mr. Newman records, in the _Zoologist_ (p. 2356), an actual testimony which he considers, "in all respects, the most interesting natural-history fact of the present century." He writes: "Captain the Hon. George Hope states that when in H.M.S. 'Fly,' in the Gulf of California, the sea being perfectly calm and transparent, he saw at the bottom a large marine animal with the head and general figure of the alligator, except that the neck was much longer, and that instead of legs the creature had four large flappers, somewhat like those of turtles, the anterior pair being larger than the posterior; the creature was distinctly visible, and all its movements could be observed with ease; it appeared to be pursuing its prey at the bottom of the sea; its movements were somewhat serpentine, and an appearance of annulations, or ring-like divisions of the body, was distinctly perceptible. Captain Hope made this relation in company, and as a matter of conversation. When I heard it from the gentleman to whom it was narrated, I enquired whether Captain Hope was acquainted with those remarkable fossil animals _Ichthyosauri_ and _Plesiosauri_, the supposed forms of which so nearly correspond with what he describes as having seen alive, and I cannot find that he had heard of them; the alligator being the only animal he mentioned as bearing a partial similarity to the creature in question." Unfortunately, the estimated dimensions of this creature are not given. That negative evidence alone is an unsafe basis for argument against the existence of unknown animals, the following illustrations will show: During the deep-sea dredgings of H.M.S. _Lightning_, _Porcupine_, and _Challenger_, many new species of mollusca, and others which had been supposed to have been extinct ever since the chalk epoch, were brought to light; and by the deep-sea trawlings of the last-mentioned ship, there have been brought up from great depths fishes of unknown species, and which could not exist near the surface, owing to the distension and rupture of their air-bladder when removed from the pressure of deep water.