The most likely marriage of John Myers was in 1842 Q1 Blackburn [vol 21 page 13]. Unfortunately the are four possible names for his wife. After comparing these and whether they were alive at the time of the 1861 census the mostly like wife was Mary Cattral. If she was his wife she must have died between 1847 (birth of daughter Mary Ann) and 1861 (census). No Blackburn death of a Mary Myers was found during this period. There are a number of deaths, at other locations, within Lancashire that could be her. A copy of the marriage details might resolve this matter.