Magento $ this-> getChildHtml（'topMenu'）不显示菜单

I am working on a redevelopment of a Magento site.

I try to display the menu, and i use this in :

<?php echo $this->getChildHtml('topMenu'); ?>

In the page.xml the reference is:

<block type="page/html_header" name="header" as="header">

            <block type="core/text_list" name="top.menu" as="topMenu" translate="label">
                <label>Navigation Bar</label>
            </block>

 </block>

Why the menu is not displayed I don't know..

Regards

It must be like this way in page.xml :

<block type="core/text_list" name="top.menu" as="topMenu" translate="label">
   <label>Navigation Bar</label>
   <block type="page/html_topmenu" name="catalog.topnav" template="page/html/topmenu.phtml"/>
</block>