Regarding inhumation jars, my Arts Editor asks:
How does this differ from an ossuary? Or is an ossuary just one type of inhumation jar?
From the article:
… inhumation jars, which are buried ceramic vessels containing bones.
And from Wikipedia’s article on ossuaries:
An ossuary is a chest, box, building, well, or site made to serve as the final resting place of human skeletal remains. They are frequently used where burial space is scarce.
An inhumation is another word for interment or burial, so I think the difference is that an ossuary is above ground.