A high-grade ore sample from the Cu-Zn-Au Photo Lake volcanogenic massive sulfide deposit (Flin Flon-Snow Lake greenstone belt, Manitoba, Canada) contains a Bi-Ag sulfo-selenide situated approximately in the middle of the S-Se substitution range (Se~0.86 apfu, S~1.05 apfu). These new data, combined with a literature compilation of all publicly available matildite and bohdanowiczite mineral chemistry data, reveal a nearly complete range of S-Se substitution between these two minerals, with only the section between BiAgSe 0.78 S 1.18 and BiAgSe 0.25 S 1.75 -about a quarter of the full S-Se range -not documented. These findings suggest that a complete solid solution series between matildite and bohdanowiczite may exist, as previously suspected and in a manner similar to the galena -clausthalite complete solid solution series.