子元素的jquery选择器

循环通过最低级别的“li”元素的正确方法是什么?

<div id="mainnav">
    <ul>
        <li>
            <ul>
                <!-- These are the elements I want to loop through -->
                <li>
                </li>
                <li>
                </li>
                <li>
                </li>
                <!-- End These are the elements I want to loop through -->
            </ul>
        </li>
    </ul>
</div>

jQuery("#mainNav > ul > li > ul > li").each(function () { 

});