unix mount command

i have the following setup. I have a HP-UX box - which is my production - never down server. I am backing up to tape, but have started backing up to a linux fedora box with a 750gb drive. i did this to eventually make it so that if the HP-UX goes down - we could switch to the fedora box until the HP-UX box comes back up. fortunetly i only need two directories on the HP box to accomplish this, i'll call them directoryA and directoryB. I can mount directoryA to the linux box because it's being exported in the /etc/exports. both directoryA and directoryB are on the root of the HP box. so in /etc/exports its

/directoryA -anon=243
/directoryB/anotherdirectory -anon=65534

i can mount and use rsync for directoryA and it works great. however for directoryB, i just want to mount directoryB to the fedora box, because the other directory isn't what i need to keep things running. i have successfully mounted /directoryB/anotherdirectory to the fedora box just to confirm it can be done.
when i try to just mount directoryB

sudo mount HPUX:/directoryB /mountdirectory

i get

access denied by server while mounting HPUX:/directoryB

in the sudo mount command for HPUX i actually use the HPUX's boxes IP address. I am assuming that i can't mount because in /etc/exports it's listed as /directoryB/anotherdirectory
i tried adding just /directoryB in /etc/exports - but HPUX complains that directoryB is already listed.
Is there some other way to mount just directoryB to my Fedora box so i can run rsync on it?