[Dan. hval-ros]. The Trichecus rosmarus, a large amphibious marine animal, allied to the seals, found in the Arctic regions. Its upper canines are developed into large descending tusks, of considerable value as ivory. It is also called morse, sea-horse, and sea-cow. This animal furnished Cook, as well as our latest Arctic voyagers, with Arctic beef. The skin is of the utmost importance to the Esquimaux, as well as to the Russians of Siberia, &c.