Which cryptocurrencies are regulated by the SEC?

Could you elaborate on which specific cryptocurrencies are currently subject to regulation by the U.S. Securities and Exchange Commission (SEC)? It's important to note that the SEC's jurisdiction over cryptocurrencies is evolving, and the regulatory framework is still developing. However, there have been instances where the SEC has classified certain cryptocurrencies or token offerings as securities, subjecting them to the SEC's regulatory authority. Are there any specific cryptocurrencies that have been explicitly identified by the SEC as falling under its regulatory umbrella? Additionally, how does the SEC determine whether a cryptocurrency or token offering constitutes a security? I'd appreciate a concise yet thorough explanation of the SEC's current approach to regulating cryptocurrencies.