Eurail between Paris and St Malo

Yes-even via more as 1 route. Its all SNCF, the big main (and often strike-happy) French national railways and they very much accept passes. THey also want you to REServe a seat in their prestigious hi-speed TGV trains-if you are in FR a few days before, easy to do at a machine, or if the fear for full trains is so overwhelming big-try to call them.

BTW- EUrail does not run any train and you will never see it-its just a coöperation since nearly 80 yrs of the assorted European national railways. These are thus also the ones to turn to for advice or ´service´