do you have a namespace on your xml?
if not, don't specify one
from original example
SELECT EXTRACTVALUE(VALUE(x), '/CHILD') AS VALUE
FROM xmltab, table(XMLSEQUENCE(EXTRACT(xmltype(xmltxt), '//CHILD'))) x
with your second example
SELECT EXTRACTVALUE(VALUE(x), '/item') AS VALUE
FROM clobxml, table(XMLSEQUENCE(EXTRACT(xmltype(xmltxt), '//animals/item'))) x