classless in-addr.arpa

[Guido Fortunati]

Hello,
I am trying to set up a classless in-addr.arpa delegation.
We were told to set up a 0/27.61.74.216.in-addr.arpa zone
and here is what i added to named.conf:

zone "0/27.61.74.216.in-addr.arpa" {
        type master;
        file "61.74.216.in-addr.arpa";


and this is what the zone file looks like:

$TTL    1800
@               IN SOA  mydns1..      mydns2.(
                        2002031800 ; serial
                        3600 ; refresh
                        900 ; retry
                        1209600 ; expire
                        43200 ; default_ttl
                        )
               IN      NS       mydns.
               IN      NS       mydns2.
1       IN      PTR     2600.irv-ca.us.whatever.
2      IN      PTR     wor2d.
3      IN      PTR     word.
4      IN      PTR     word.
5      IN      PTR     word.



what is wrong with this?.. i see our provider trying to do AXFRs, i guess
they pull down the information from our ns and then spread it around the
world, but i dont think this zone is right, i think i need some $ORIGIN?
sorry for the ignorant question, any help will be strongly appreciated.

-guido