Paul Monfils asks why so many generic names named for people end in the
feminine suffix -a. Like most taxonomic questions, this one has a history
behind it.
 
In the early days of taxonomy, virtually all taxonomists were male and
wrote in Latin. If I had written on shells at that time, I would have
probably been referred to as Rindsbergius or Rindsbergus instead of
Rindsberg. Generic names were capitalized, but not italicized. Under the
circumstances, how would you distinguish a person's name (Rindsbergius)
from a generic name (Rindsbergius)? They would look and sound alike.
Imagine having a snail named "Rindsbergius" and then being called by the
snail's name: The students would love it, but the joke would get stale
fast. Better to name the snail as Rindsbergia or Rindsbergium, or even
better as "little Rindsberg": Rindsbergiella, Rindsbergina, etc.
Incidentally, Rindsberg is pronounced with a short "i", as in "little", not
as in "mind".
 
Chauvinism probably also entered into this consideration. Male botanists
may have preferred to give feminine endings to the names of showy flowers,
for instance (Bougainvillea, Begonia, Kalmia, Dahlia, etc.).
 
By the time women were admitted to the hallowed halls of taxonomy, it must
have seemed natural for generic names based on personal names to end in -a,
not -us. But there is no rule demanding this.
 
As to generic names ending in the neuter plural -a, there are none. All
generic names must be in the nominative singular (ICZN, Article 11g).
 
Andrew K. Rindsberg
Geological Survey of Alabama