CONTENTS 



PAGE 



Introduction 1 



I. EXTERNAL FORM 



External Form of Heptanchus maculatus 5 



External Form of Elasmohranchs in General 8 



Transitional series i • • 9 



External form in its development 10 



Form and position of adult fins 12 



External form of fin and its bearing on function 12 



Form of fin in its beginning 14 



Bibliography 17 



II. INTEGUMENT 



Integument of Heptanchus maculatus 23 



Modified scales 25 



Integument of Elasmobranchs in General 26 



Gland cells 28 



Glands of claspers 28 



Poison glands of sting ray 28 



Light organs 29 



Placoid scales 30 



Finer anatomy of scale 32 



Modification of scales 33 



Fin spine 33 



Saw tooth 35 



Sting 35 



Gill rakers 37 



Stomodeal denticles 38 



Teeth as modified scales 38 



Bibliography 39 



III. ENDOSKELETON 



Endoskeleton of Heptanchus maculatus 43' 



Axial skeleton 43 



Skull 43 



Visceral skeleton 44 



Spinal column ■ ... 47 



Appendicular skeleton 49 



Skeleton of paired fins 50 



Skeleton of unpaired fins 51 



Dorsal fin 51 



Caudal fin 51 



Anal fin 52 



Endoskeleton of Elasmobranchs in General 53 



Axial skeleton 53 



Skull 53 



Cranium 53 



Visceral skeleton 62 



Extravisceral arches 67 



Spinal column 69 



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