Record type and ROW type in pl/pgsql functions

Hello,
I'm runninig latest version (7.4.2) of postgresql on OpenBSD 3.4.

I created table

CREATE TABLE "billing"."mail_relayhosts" (
"id" SERIAL,
"hosts" CIDR,
"description" VARCHAR(255),
CONSTRAINT "mail_relayhosts_pkey" PRIMARY KEY("id")
);

and made pl/pgsql function:

CREATE OR REPLACE FUNCTION "billing"."mail_get_relayhosts" () RETURNS varchar AS'
declare
hosts_str mail_relayhosts%ROWTYPE;
hst varchar(256);
begin
hst:=''127.0.0.1'';
FOR hosts_str IN SELECT hosts from mail_relayhosts LOOP
hst:=hst||'':''||text(hosts_str.hosts);
END LOOP;
return hst::varchar;
end;
'LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

when I call this finction I get error:
ERROR: invalid input syntax for integer: "217.23.184.0/24"
Actually there is a record in mail_relayhosts.

but if make function like this:

CREATE OR REPLACE FUNCTION "billing"."mail_get_relayhosts" () RETURNS varchar AS'
declare
hosts_str RECORD;
hst varchar(256);
begin
hst:=''127.0.0.1'';
FOR hosts_str IN SELECT hosts from mail_relayhosts LOOP
hst:=hst||'':''||text(hosts_str.hosts);
END LOOP;
return hst::varchar;
end;
'LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

everything works fine. Is there any difference between rowtype and
record?
I understand rowtype has predefined structure, that record
has not.
But by manual description in Looping Through Query Results
as variables can be taken both of them:
FOR record_or_row IN query LOOP
statements
END LOOP;

But in practice only record type can be taken.
Is it bug or I've something missed?

Best regards, Dinar Talipov