use of %TYPE

Can I use %TYPE in a function definition a la:
=============================================================================
CREATE OR REPLACE FUNCTION add_usr ( Usrs.first_name%TYPE,
Usrs.middle_name%TYPE,
Usrs.sur_name%TYPE,
Usrs.sur_name_extra%TYPE,
Gens.gen%TYPE,
Emails.email%TYPE,
UsrEmailTypes.usr_email_type%TYPE )
RETURNS BOOLEAN AS '
DECLARE
var_first_name ALIAS FOR $1;
var_middle_name ALIAS FOR $2;
var_sur_name ALIAS FOR $3;
var_sur_name_extra ALIAS FOR $4;
var_gen ALIAS FOR $5;
var_email_addr ALIAS FOR $6;
var_email_addr_type ALIAS FOR $7;
BEGIN
RETURN ''f'';
END;
' LANGUAGE 'plpgsql';

=============================================================================

Also, does pgsql keep case in the table and column names? phpPgAdmin shows no case on tables I
created with case.