Crassiscala subterranea was a small wentletrap sea snail moving over the London Clay seabed. Wentletraps are carnivorous gastropods associated with cnidarians, and London Clay epitoniids are interpreted as having browsed on animals such as sea anemone or coral relatives rather than grazing algae.

That ecology is inferred from its family and from the wider London Clay mollusc community because the feeding animal itself is not preserved. Its presence shows that the seabed supported not just shellfish and deposit feeders but also small specialist predators exploiting other invertebrates.