The quatrefoil frame at the bottom of the March calendar page contains a bull, the zodiacal emblem of Taurus. Medieval images of Taurus show the animal in profile, with one or sometimes two legs bent to show that he is walking. Here the head of the bull seems to be carried low; this may derive from the Hellenistic tradition of showing Taurus as a charging bull. (Teresa Perez-Higuera, Medieval Calendars, 1997).
In his Etymologiae, the seventh-century encyclopedist Saint Isidore asserts that Taurus, like Aries, was included among the constellations in honor of Jupiter, who took the form of a bull in the rape of Europa.
The thirteenth-century Breviari d’amor gives a symbolic interpretation, and identifies Taurus as an ox, rather than a bull:
The second sign is called Taurus, which means ox, because of these properties: just as the ox, in ploughing and passing over the land, makes it fertile and good and causes it to bear fruit, so also the sun, when it passes through this sign, warms the cold earth, and thereby makes things grow, multiply and bear fruit during this period, and does so quickly. It is also called Taurus because just as the bull is stronger than the ram, so the sun is stronger and more vigorous than when it runs through the sign of Aries or the ram, which is where the sun passes before going through the sign of Taurus.
—Medieval Calendars, 1997