How revoke DEQUEUE on SRVQUEUE from PUBLIC during SRVQUEUE does not exist ?

SQL> select GRANTEE, PRIVILEGE, TABLE_NAME

from DBA_TAB_PRIVS

where GRANTABLE = 'YES'

and GRANTEE = 'PUBLIC'

and TABLE_NAME = 'SRVQUEUE';

GRANTEE     PRIVILEGE   TABLE_NAME

---------            ---------           -------------

PUBLIC      DEQUEUE     SRVQUEUE

As we can see , PUBLIC have the privilege DEQUEUE on SRVQUEUE, but when i revoke it as below, there is an error.

SQL> revoke DEQUEUE on SRVQUEUE from PUBLIC;

revoke DEQUEUE on SRVQUEUE from PUBLIC

       *

ERROR at line 1:

ORA-00990: missing or invalid privilege

When i desc SRVQUEUE , it returns object does not exist.

SQL> desc SRVQUEUE;

ERROR:

ORA-04043: object SRVQUEUE does not exist

I have two question:

Question 1: How can i revoke the privilege from PUBLIC ? And if i revoke this privilege from PUBLIC, the ORACLE database will cause exception or not ?