As I read Genesis, I find the description of the serpent to be not that of Satan, but of a snake. What is the Jewish position on this subject: Snake or devil? And, if the devil, why should the snake be given the blame?

You ask a very good question. The Nachash (snake) is analogous to Satan, which is really the yetzer hara, (i.e. the evil inclination) that is found within each of us. The yetzer hara/Satan itself is NOT evil. It has been given a task to do by G-d. It will do its job and try to tempt us toward that which is not Godly, but it wants to be defeated. It is merely acting as a tool of G-d to allow us to resist the forbidden fruit in order to raise ourselves spiritually.

If so, why was the Nachash punished if it was only doing its job?

That happens to be a very difficult question to answer, and it is probably beyond my understanding; but I do have a theory: It may be a lesson for us that inappropriate behavior brings, by definition, unpleasant consequences. G-d created animals for the benefit of people (e.g. for food and clothing), and this might even include lessons on proper conduct.

Regards, Eliahu Levenson