Vacant residences or animal remains

There is a slightly occult feel to this description in William T. Broad's Science Times piece about Peter Rona's two-mile-deep diving quest:

Dr. Rona has found that P. nodosum thrives in restricted areas of Atlantic seabed. Its only visible feature consists of tiny holes arranged in six-sided patterns that look curiously like the hearts of Chinese checkers boards. He has photographed thousands of the hexagons and found that large ones have 200 or 300 holes.