CHAPTER X. The Relationship of Ammocoetes to the Most Ancient Fishes--the

THE RELATIONSHIP OF AMMOCOETES TO THE MOST ANCIENT FISHES--THE OSTRACODERMATA

The nose of the Osteostraci--Comparison of head-shield of Ammocoetes and of Cephalaspis--Ammocoetes only living representative of these ancient fishes--Formation of cranium--Closure of old mouth--Rohon's primordial cranium--Primordial cranium of Phrynus and Galeodes-- Summary 326