Hermes Kriophoros (“Ram-bearer”), Roman copy of the Imperial Age, from a Greek original of the V century B.C., now in the Ancient Sculpture Museum (Museo di Scultura Antica Giovanni Barracco) in Rome. Hermes, son of Zeus and of the nymph Maia, was the god of the shepherds and of the travelers, inventor of the heap of stones which pointed out the path through unknown countries, but he was also protector of merchants and thieves, psychopomp (“guide of the souls”) and messenger of Zeus. The common trait in all these functions is the fact that Hermes travels in an intermediary space, a space of mobility and of the unexpected, in which he is the mediator, a medium, providing a communication between different realms. Spokesman for the gods and leader of the dead, he ensures the passage and transition even where the humans do not see but impenetrable borders (Kahn-Lyotard 1981).
As patron of pastures and of herds, he was the favorite god of Arcadia, a country covered by pasturage and woodlands. God of lonely places and of cattle, Hermes was regarded as the father of Pan, and, in his quality of protector of the flocks, he was often represented with a sheep or a ram on his shoulders. This representation borrows a diffused motif from the Near East, that of the Sumerian god Dumuzi for example, and shall be probably an iconographic prototype for the subsequent image of the Good Shepherd in early Christian art (Mastrocinque 2005).
The ram was a symbol of fecundity and wealth: the most renowned in Greek mythology was the golden ram which was disputed among the pretenders to the throne of Mycenae. The wonderful animal brought in flight the twins Phrixus and Helle to the remote land of Colchis, where its golden fleece was preserved, guarded by a dragon. Jason gathered a wide array of heroes, who embarked on the ship Argo and faced many risks and adventures to recover the famed Golden Fleece.

[Source: http://en.wikipedia.org/wiki/Kriophoros]