Securities purchased pursuant to the provisions of this chapter shall be held by the public official, municipal corporation or other political subdivision or public body or its custodial agent who may not otherwise be a counterparty to the investment transaction. Securities held on the books of the custodial agent by a custodial agent shall be held in the name of the municipal corporation, political subdivision or other public body subject to the public body’s order of withdrawal. The responsibilities of the public official, municipal corporation, political subdivision or other public body shall be evidenced by a written agreement that shall provide for delivery of the securities by the custodial agent in the event of default by a counterparty to the investment transaction. As used in this section, “counterparty” means the issuer or seller of a security, an agent purchasing a security on behalf of a public official, municipal corporation, political subdivision or other public body or the party responsible for repurchasing securities underlying a repurchase agreement. The provisions of this section shall not apply to (i) investments with a maturity of less than 31 calendar days or (ii) the State Treasurer, who shall comply with safekeeping guidelines issued by the Treasury Board or to endowment funds invested in accordance with the provisions of the Uniform Prudent Management of Institutional Funds Act, Chapter 11 (§ 64.2-1100 et seq.) of Title 64.2.