Thus Trautschold gives a number of instances with Ammonites, and Hilgendorf has described a most curious case of ten graduated forms of Planorbis multiformis in the successive beds of a fresh-water formation in Switzerland.
horrela, Trautschold-ek Ammonites-en zenbait adibide aipatzen ditu, eta Hilgendorf-ek Planorbis multiformis-en hamar forma mailakaturen kasu oso bitxi bat deskribatzen du, Suitzako ur gezatako formazio baten hurrenez hurreneko geruzetan.