The Cambridge natural history, Vol. 03 (of 10)Note 6 — Chapter I · INTRODUCTION—POSITION OF MOLLUSCA IN THE ANIMAL KINGDOM—CLASSIFICATION—ORIGIN OF LAND AND FRESH-WATER MOLLUSCAReading editionπτερόν, wing.◇Copy noteReturn to CHAPTER I INTRODUCTION—POSITION OF MOLLUSCA IN THE ANIMAL KINGDOM—CLASSIFICATION—ORIGIN OF LAND AND FRESH-WATER MOLLUSCA