ATDTDA (14) references p 378

[David Morris]

Also, on a somewhat related note, the tombs of New Orleans were from
the beginning a sort of communal burying place, with "one-person"
sized tomb often serving more than one family over a period of years:

http://itotd.com/articles/453/new-orleans-cemeteries/

A Bone in the Oven
The first cemetery in New Orleans designed for aboveground burial was
the St. Louis #1 cemetery, which opened in 1789. Some accounts claim
it was modeled after Paris's famous Père-Lachaise cemetery, and there
can be no doubt that the two bear a strong resemblance to each other.
But Père-Lachaise wasn't used as a cemetery until 1804, so that
resemblance may be coincidental. Be that as it may, there is a
significant difference that goes beyond the superficial similarities.
At Père-Lachaise, the visible structures are, for the most part, just
monuments; the bodies themselves are usually placed in vaults in the
floors of the tombs.  In New Orleans, however, bodies are usually
placed inside the walls of the tombs. Because of the hot, subtropical
climate, the tomb then effectively becomes an oven, and the high heat
causes the body to decompose rapidly in a process that has been
compared to a slow cremation. Within about a year, only bones are
left.

Just as an oven would not be constructed to bake a single loaf of
bread, the tombs in New Orleans cemeteries are used again and again.
The specifics vary depending on the exact design of the tomb, but a
typical scenario is that after a year, the bones of the departed are
swept into an opening in the floor of the tomb, which is then ready
for its next occupant. It is a common practice to bury all the members
of a family—or multiple families—in the same tomb, with names and
dates added to a plaque or headstone as necessary. This procedure is
not only sanitary and efficient; it also avoids the problem of growing
real estate needs as time goes on.