Unknown final note shape / object. What it is?

[Nils Gey]

I stumbled upon this picture of notation and I've never seen the final note (in 
each voice, the right page voices have a slightly different version)
http://anaigeon.free.fr/mes_facs/fsjosq.jpg

From the position it must be a longa, the fermata over it indictates the same. 
Best visible on the top left version is that there is indeed the right-handed 
stem from a longa at the end of this symbol.

Has anyone seen this in a different context? I would like to see more pictures 
or versions.

Btw. if you know any other strange or seldom used notation symbols please let 
me know :)

Greetings,

Nils