Chapter X

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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