[ESS] Can't start SPLUS 7 under ESS

[glynn, bill (Performance ENG)]

     I have recently installed SPLUS 7 on a Sun Ultra 60 running Solaris
2.8.
I have Emacs 21.3.3 and ESS 5.2.10 installed.  When I installed ESS I added

         "PATH_TO_ESS/ess-5.2.10/lisp/ess-site"

to my .emacs file, where PATH_TO_ESS is the path to ESS 5.2.10, and

   (setq-default inferior-S+7-program-name "/usr/local/bin/Splus")

where Splus is the script which starts SPLUS 7.  I have a similar statement
for
SPLUS 6

   (setq-default inferior-S+6-program-name "/swapps/splus/v6.2.1/cmd/Splus")

Using M-x S+6 I can run SPLUS 6 under ESS, but when I try M-x S+7 I get

    M-x S+7 [No match]

I assume this means that Emacs does not know how to interpret S+7, but I
don't
know why.  

I can start SPLUS 7 from the command line using /usr/local/bin/Splus 

Any help will be greatly appreciated.

Bill Glynn