Will the unicorn be willing to serve thee, or abide by thy crib? This is an unfortunate translation, since there is no word etymologicallly correspondent to "unicorn" in the original. The word used is rem or reyrn; and the rem is distinctly said in Deuteronomy 33:17 to have "horns."
All that is said of the rim in Scripture points to some species of wild cattle, and recent critics are almost universally agreed thus far at any rate. Assyrian investigation carries us a step further.
It is found that the wild bull so often represented on the monuments as hunted by the Ninevite monarchs was known to the Assyrians by the name of rimu or rim. Careful examination of the sculptures has resulted in the identification of this animal with Bos primigenius, an extinct species, probably identical with the urus of the Romans, which Caesar saw in Gaul, and of which he has left a description.
"These uri," he says, "are scarcely less than elephants in size, but in their nature, colour, and form are bulls. Great is their strength, and great their speed; nor do they spare man nor beast, when once they have caught sight of him.
… Even when they are young, they cannot be habituated to man and made tractable. The size and shape of their horns are very different from those of our own oxen" ('De Bell. Gall.,' 6.28).