Rigby, J. Keith, Sponges of the middle cambrian Burgess shale and Stephen formations, British Columbia / J. Keith Rigby, Desmond Collins. - 155 páginas : ilustraciones. - ROM contributions in science; no. 1 . ISBN: 088854443X Subjects--Topical Terms: ESPONJAS--FOSILES.PALEONTOLOGIA--CAMBRICO. Dewey Class. No.: 563.4