ORA-27475 on dbms_audit_mgmt.drop_purge_job

I am having trouble dropping an audit purge job and can't quite figure out what I'm doing wrong.....  It's an 11.2 database.  I have 2 jobs listed, I can delete one of them (SLS_D_AUDIT_PURGE_XML), but not the second job (SLS_DAY_AUD_PURGE_XML).  It's the second job tha I need to remove.

SQL> exec dbms_audit_mgmt.drop_purge_job('SLS_DAY_AUD_PURGE_XML');
BEGIN dbms_audit_mgmt.drop_purge_job('SLS_DAY_AUD_PURGE_XML'); END;

*
ERROR at line 1:
ORA-27475: "SYS.SLS_DAY_AUD_PURGE_XML" must be a job
ORA-06512: at "SYS.DBMS_ISCHED", line 213