Mass. Gen. Laws ch. 106, § 9-328
The following rules govern priority among conflicting security interests in the same investment property:
(2) Except as otherwise provided in paragraphs (3) and (4), conflicting security interests held by secured parties each of which has control under Section 9–106 rank according to priority in time of:
(B) if the collateral is a security entitlement carried in a securities account and: