UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 13, No, 6, pp. 147-166, pis. 8-9, 4 text figures May 23, 



A.; 



THE ANATOMY OF HETERODONTUS 

 FRANCISCI 



I. THE EXOSKELETON 



BY 



J. FEANK DANIEL 



CONTENTS 



PAGE 



A. Introduction 148 



B. The exoskeleton, or placoid scales 149 



I. The preparation of scales for study 149 



II. Types of scales 150 



III. The form of the ventral scale , 150 



1. Modifications in form of the ventral type of scale 151 



IV. The form of the dorsal scale 153 



1. Modifications in form of the dorsal type of scale 154 



V. Complexity of the dorsal scale 156 



VI. The form of the caudal scale 158 



VII. Dorso-ventral transitional areas 158 



VIII. Variations in size of scales 160 



1. Variations in size due to time of origin 160 



(a) The embryonic scale or spinule 160 



(b) Secondary scales 160 



2. Variations in size correlated with function 161 



(a) Marginal scales as modified by function 161 



(b) Stomodeal denticles in relation to function 162 



C. Literature cited 163 



D. Explanation of plates 164 



