MORPHOLOGY OF THE MYXINOIDEI. 



I. SKELETON AND MUSCULATURE?- 

 HOWARD AYERS and C. M. JACKSON. 



CONTENTS. PAGE 



Introduction 185 



A. Skeleton (in general) 189 



a. Endoskeleton (general) Intermuscular Septa 190 



a. Notochord, Structure, and Position, Sheaths, Neural Canal 190 



j8. Skeleton of Head Region (skull as a whole) 193 



1. Membranous Cranium 194 



2. Parachordals, Auditory Capsules, and Trabeculae 194 



3. Hypophysial Plate and Canal 196 



4. Olfactory Capsule and Nasal Tube 196 



5. Cornual and Subnasal Cartilages 200 



6. Labial and Tentacular Cartilages 201 



7. Basal Plate and Mandibular Cartilages 202 



8. Palato-Pterygoid and Epi-Hyoid Arches :.... 207 



9. Anterior Branchials and Velar Cartilages 209 



10. Gill and Muscle Cartilages 212 



7. Caudal Region 214 



1. Median Dorsal and Ventral Bars, Neural Ring 215 



2. Fin Rays 215 



3. Cloacal Cartilage 217 



b. Exoskeleton 217 



c. Remarks on Homologies 



B. Musculature 



C. Explanation of the Plates 224 



Introduction. 



It is now sixty-four years since Johannes Muller published 

 the first part of his " Anatomie der Myxinoiden." Since that 

 time almost nothing has been added to our knowledge of the 

 anatomy of these interesting and important forms of ancestral 



1 Contributions from the Morphological Laboratory of the University of 

 Cincinnati. 



185 



