H. verrilli colonies are calcified and encrusting. Individual zooids are regular in shape, and generally quadrangular. Zooids measure an average of 0.40 X 0.29 mm, but older colonies grow as large as 0.47 X 0.39 mm. A slightly raised rim separates zooids from each other. Ten to twenty regularly-spaced pores perforate the frontal surface of individual zooids. The orifice is rounded distally, with a slightly curved proximal portion. There is often an umbo just inferior to the orifice. The lophophore measures approximately 0.428 mm in diameter and bears 12 tentacles. avicularia are highly variable, or absent in some colonies. If they are present, they may occur on either side, or on both sides of the orifice. Avicularia may be narrow; ovoid, or have round bases with triangular mandibles. The narrow type is generally directed proximolaterally; the other types can have a variety of orientations. Living specimens from the IRL area are ivory or beige in color. However, specimens from other areas vary from shades of yellow to red.