The following is the entry for Erasmus Ommanney in William O'Byrnes 1849 'Naval Biographical Dictionary'.
OMMANNEY. (Captain, 1846.)Erasmus Ommanney is son of the late Sir Fras. Molyneux Ommanney, Kt., M.P. for Barnstaple, the well-known Navy Agent; and nephew of Vice-Admiral Sir John Acworth Ommanney, K.C.B.
This officer entered the Navy 15 July, 1826; passed his examination in 1833; and obtained his first commission 10 Dec. 1835. His succeeding appointments were – 28 Dec. 1835, to the Cove, Capt. Jas. Clark Ross, employed on particular service – 7 Oct. 1836, to the Pique 36, Capt. Henry John Rous, attached to the force off Lisbon – and, 18 Oct. 1837, to the Donegal 78, as Flag-Lieutenant to his uncle Sir J. A. Ommanney, on the station last named, where he continued during a further period of three years. He was advanced to the rank of Commander 9 Oct. 1840; and from 28 Aug. 1841 until paid off at the close of 1844, was employed in that capacity in the Mediterranean on board the Vesuvius steam-sloop. He has since been on half-pay. His promotion to the rank he now holds took place 9 Nov. 1846.
Capt. Ommanney married, 27 Feb. 1844, Amelia Mary, eldest daughter of Sam. Smith, Esq., of H.M. Dockyard, Malta. Agents – Messrs. Ommanney.