Figure 3.10:

The four main types of cheilostome ooecium: (A) calloporiform; (B) escharelliform; (C) Lepralielliform; (D) microporelliform. Each is depicted as a hypothetical median longitudinal section through two autozooids (polypide not shown), the one on the left producing the ooecium and the one on the right constituting the maternal zooid that produces the embryo to be housed in the ooecium. Solid lines = skeletal components; broken lines = cuticular wall/layer, with or without associated epithelium. There are variations of, and departures from, these four main types. Note that, in the depiction of the lepralioid ascus in D, the roof of the ascus is not depicted, except beneath the pseudopores. According to Cheetham and Cook (1983), the cuticular roof of the ascus lines the underside of the frontal shield, but it can be lacking, or, in a few species, is separated from the underside of the frontal shield.