There have been, at some periods, shallow seas "inside" continents. Much of present-day North America was covered by an epicontinental sea called the Sundance Sea during the Jurassic period. In the Cretaceous an even larger area was covered by the Western Interior Seaway. A modern example is the Baltic Sea. The North Sea is not an inland sea, but it does sit on continental shelf, and so is epeiric (that is what the word means). The Hudson Bay is often considered an epeiric sea because its depth averages 100ft (30 m) whereas, for example, the Bay of Bengal is 2,600 metres (8000 ft) deep. So epeiric seas are on the continental plate, as are inland seas. The inland seas, however, are more enclosed.