this time in history, roughly around 4000 B.C., the Sun's position along the Zodiac on the first day of spring, or Vernal Equinox, was in that constellation we now recognize as Taurus, the Bull. So for many centuries Taurus was to be the first and most important constellation of the Zodiac. Some have suggested that Taurus may have been the first Zodiac constellation invented.
"Gradually the white bull wandered closer to the sea and when near the beach ran into the water and began swimming towards the island of Crete. By this time is was to late for Europa to climb off. When the two arrived to Crete, Zeus changed himself back into his own form. Realizing that he could not marry Europa himself, Zeus gave her in marriage to Asterius, king of Crete."(Chernal, 5-6)
When you look for Taurus in the sky, you only see his front half. The explanation is that his hind quarters are underwater since he is quite busy carrying Europa across the sea to Crete.