N.Y. Real Prop. Acts. Law § 418

§ 418. Assignment of mortgage, lease, or other lien or charge. The\nholder of any mortgage, lease, or other lien or charge on registered\nproperty, in order to transfer the same or any part thereof, shall\nexecute an assignment of the whole or any part thereof; and upon such\nassignment being filed in the office of the registrar, the registrar\nshall enter in the title book a memorial of such transfer with a\nreference to the assignment by its file number; he shall also note upon\nthe instrument on file in his office intended to be transferred, and\nupon the registration copy thereof produced, the number of the\ncertificate on which the memorial is entered, with the date of the\nentry.\n