Noreen, it's not the kind of melodeon with which you are probably familiar. It's the big boxy wooden thing right in the middle of the picture with the woman sitting behind it. It's related to the kind of melodeon you know about in that it is a free reed instrument with a bellows. But it's in a piano-like cabinet and the bellows are operated with foot pedals. Here are some other pictures with some information and dates...

http://www.kshs.org/cool/coolmel.htm

http://www.cuc.claremont.edu/fiske/melodeon.htm

http://www.reedorgan.com/portfolio/pratt.1865.white.html