Riddle 32: Ship

This world is beautified in various ways, decked with adornments. I saw an artful work go forth, excellent in journeys, grind against the sand, move with a cry; the strange creature had not sight nor hands, shoulders nor arms; the curious thing must move on one foot, go quickly, pass over the plains; it had many ribs; its mouth was in the midst, useful to men; it brings to the people provision in plenty, bears food within it, and each year yields to men a gift of which men, rich and poor, make use. Tell, if thou canst, O sage, wise in words, what that creature is.