|MadSci Network: Earth Sciences|
You are correct. Maritime refers to air masses that form over water, and continental refers to air masses that form over large land areas.
When an air mass forms over an area and stays there for awhile, it takes on features of that area. An air mass forming over northern Canada in the winter would be cold and dry – a Continental Polar air mass.
Here is a great web site that will teach you all about air masses: http://www.islandnet.com/~see/weather/elements/airmasses.htm
Here is a picture showing some air mass source regions for North America
(from the above web site).
Try the links in the MadSci Library for more information on Earth Sciences.