使用extra-icon的问题

<nav class="mui-bar mui-bar-tab">  
            <a id="defaultTab" class="mui-tab-item mui-active" href="tab-webview-subpage-about.html">  
                <span class="mui-icon  mui-icon-chatbubble"></span>  
                <span class="mui-tab-label">message</span>  
            </a>  
            <a class="mui-tab-item" href="tab-webview-subpage-chat.html">  
                <span class="mui-icon mui-icon-contact"></span>  
                <span class="mui-tab-label">contacts</span>  
            </a>  
            <a class="mui-tab-item" href="tab-webview-subpage-contact.html">  
                <span class="mui-icon mui-icon-extra-find"><span class="mui-badge">9</span></span>  
                <span class="mui-tab-label">finding</span>  
            </a>  
            <a class="mui-tab-item" href="tab-webview-subpage-setting.html">  
                <span class="mui-icon mui-icon-gear"></span>  
                <span class="mui-tab-label">setting</span>  
            </a>  
        </nav>

如上，想引用extra-icon的find的图标，结果变成了icon里面的compose图标，是什么原因呢