Database Connect

Hi,

I installed Postgresql 7.1 (RPMs for Redhat 7.0).
When I start psql with the command 'psql mydb', everything's ok
But whan I start psql with the command 'psql mybase@myhost' I receive  :
psql: FATAL 1: Database "mybase@myhost" does not exist in system catalog

I used this syntax with Postgresql 7.03.
Is there some modifications between 7.03 and 7.1, or is it a bad config of
my server ?

Any help will be appreciated

Thank's a lot

Michael