Wikipedia
Mandolone
A mandolone is a member of the mandolin family, created in the 18th Century. It is a bass range version of the Neapolitan mandolin. Its range was not as good as the mandocello, which replaced it in mandolin orchestras, and had largely disappeared in the 19th Century.
Besides the lesser range, compared to the mandocello, the mandolone was also a quieter instrument. This was a problem, because the other instruments making up the mandolin orchestras were getting louder. In regular orchestras, it had to be heard with violins, violas and cellos, which were getting louder as well.