It's this simple at this point.
If he doesn't give you a full refund or ship you the correct snake at no cost for you then you need to leave a bad review on him. You don't need to pay anything in this matter, not even if he wanted that snake shipped back to him, it would be on him.
Then if he doesn't righ the situation, call your credit card company and state that you'd like to file a dispute and that you paid for something and you never received the product. Your company should side with you on this then that way you still get all your money back and leave him a bad review still. That's just what I would do if I were screwed over though.