UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 18, No. 10, pp. 151-170, 12 figures in text March 9, 1918 



THE MUSCULATURE OF HEPTANCHUS 

 MACULATUS 



BY 



PIEIE DAVIDSON 



CONTENTS 



PAGE 



Introduction 151 



Material 151 



Historical 152 



The musculature 152 



Pharyngeal musculature 152 



Superficial circular muscles 153 



Interarcuales 158 



Subspinalis 159 



Adductors 159 



Hypobranchials 161 



Musculature associated with the organs of special sense 162 



Appendicular musculature 163 



Musculature of the trunk 167 



Literature cited 170 



INTRODUCTION 



For several years past work has been in progress on the various 

 systems of the elasmobranch fishes in the Zoological Laboratory of 

 the University of California and at the Scripps Institution for Bio- 

 logical Research at La Jolla. Material is easily obtained and many 

 types have been studied, both of the sharks and of the rays. The 

 seven-gilled form has been of particular interest because of its sup- 

 posed generalization. 



Material 



The seven-gilled form of the Pacific coast is Heptauclius {Notorhy- 

 nchus) maculatus. It is dark gray dorsally with black spots, and light 

 colored ventrally, and may readily be recognized by the presence of 



