As is constantly the case in prophetic writings. Revelation tells of the remote past sometimes as well as the future, and in neither case could the inspired writer fully understand the meaning that was wrapped up in his sentences.
As a matter of fact, in the one case, if the writer's knowledge were of any importance, it is almost certain that he did not mean cetacean or sirenian. In the other case it is impossible to say whether he thought "bats" were included or not. It is not in the nature of things that the writer could ever have seen or even heard of a manatee or a dugong; nor is it likely that he had been a sea-farer, or could have seen any Mediterranean cetacean. As far as his own knowledge went, he probably had but a very confused idea. And if we refer to the poetic description in Psalm civ. 25, 26, we find "leviathan," though distinctly a sea creature, still one of which the writer had only a vague traditional idea, certainly not a known Mediterranean dolphin, for in Job xli. the same term is applied to the crocodile.
And perhaps the pachydermatous mammals (Nicholson, "Zoology," p. 566).
Nor should we be surprised to find (should it be so discovered) that some animals appeared after man. (Cf. "Nineteenth Century" for Dec. 1885, p. 856.)