The specimens were selected by N.B. Peake, Norwich. Many of the forms are extreme variants depending upon the nature of the sea floor upon which they lived. Many of these extreme forms, none the less, are able to develop only at particular horizons, given the appropriate bottom conditions and are thus of considerable statigraphic value. The specimens selected are those of the greatest stratigraphic value, representing as they do, extreme developments from a sometimes hypothetical central stock and do not necessarily represent an evolutionary series.
Size: various
Size: various