Content type doesn't show up on the content types list

Question

I am installing a content type as a feature, below is the content type schema. Note that it is inherited from base Item content type.

  <ContentType  ID="0x010089D9A70BCA774310BCC5DF7D0690843E"
    Name="CustomItem"
    Group="Annual Leave Request"
    Description="Custom Item Type"
    Version="0">
    <FieldRefs>
      <FieldRef ID="{F6DEF8BA-F1EF-44a5-918B-58100C5E57F9}" Name="Period" Required="TRUE" ShowInNewForm="TRUE" ShowInEditForm="TRUE"/>
    </FieldRefs>
  </ContentType>

After installing and activating the feature, the content type never shows up on the Site Content Types list. Actually there is another content type definition besides this and it inherits Workflow task content type and I can see it in the Site Content Types list.

Do you see anything wrong with the schema?