Oracle Database Discussions

I want to create a public synonym for a db link.
The existing db link name is tst.world ( which is in db links table and is working fine).

I created the following db link using the following command:

create public synonym "syn.world" for "tst.world";

It created the synonym successfully.
If I try the following, it throws error "Connection desccriptor not found".

select * from dual@syn.world;

It says "Connection desccriptor not found".

Any suggestions.

Thanks in Advance.