JB, The one that I know as Orchid Cactus is the Epiphyllum but I think there are a couple of others commonly called "Orchid Cactus" also and the blooms look a lot alike. Epiphyllum and Disocactus are a couple but I think there are more than just those two genus' that have the common name of Orchid Cactus:
http://garden.org/plants/searc...
We have some very knowledgeable folks over on the Epiphyllum forum who may be able to help determine by viewing a photo whether yours is an Epiphyllum or Disocactus, etc.:
http://garden.org/forums/view/...
