California Code, Financial Code - FIN § 6852

(a) Whenever a person holding an account in a fiduciary capacity dies and no written notice of the revocation or termination of the fiduciary relationship has been given to an association and the association has no written notice of any other disposition of the beneficial estate, the withdrawal value of the account, and interest on it, or other rights relating to it, may, at the option of an association, be paid or delivered, in whole or in part, to the beneficiary or beneficiaries.

(b) In the absence of written notice to the contrary an association may presume that each beneficiary of an account with two or more beneficiaries has an undivided equal beneficial interest in the account.