Ramban

CATTLE. These are the species that eat grass, whether domestic animals or those of the wilderness. AND BEAST OF THE EARTH. Those which eat flesh are called chayoth (beasts), and they all seek and seize prey. VAREMES’ (AND CREEPING THING). Rashi wrote: “These are creeping swarms that creep low upon the earth, appearing as though they are dragged along.” Now in this chapter we find: And over every animal ‘haromeseth’ (that creepeth) upon the earth; and it is further written, And all flesh ‘haromes’ (that moved) upon the earth perished, both fowl and cattle, and beasts, and every swarming thing that swarmeth upon the earth; also, Wherein all the beasts of the forest ‘tirmos’ (do creep forth). But the meaning of r’misah is as if it were written with the letter samech, as in The foot tirm’senah (shall tread it down), and other related expressions. He thus says of beasts and cattle, ‘romes’ (that tread) on the earth, and of creeping things that drag along, ‘remes’ (that creep) upon the ground, because they tread on the ground with their entire body.