LIST OF WOODCUTS. 



Fir,. I'AGE 



1 . Petrontyzon marinus. The skull, from the left side .... 3 



2. The brain-case, from above 4 



3. The nasal capsule 5 



4. Dissection of the anterior part of the body, from the 



left side 9 



5- The urinogenital sinus and adjacent paris II 



6. Transverse section through the branchial region .... 12 



7. Transverse section through the abdominal region ... 14 



8. Transverse section through the caudal region .... 17 



9. The brain, from above 24 



10. Raja nasuta. The skeleton, from beneath 30 



11. Part of the vertebral column 31 



12. A trunk vertebra, from the front 32 



13. Longitudinal section of trunk vertebra 33 



14. A caudal vertebra, from the front 34 



15. The gall-bladder and bile-ducts 49 



16. The portal vein 51 



17. The venous system 53 



1 8. Raja batis. Urinogenital organs (male) 55 



19. Urinogenital organs (female) 57 



20. Raja nasuta. The arterial system 62 



21. Diagram of the heart and chief blood-vessels 63 



22. The nervous system, from above 71 



23. Raja batis. The brain, from beneath 73 



24. Longitudinal section of the brain 74 



25. The brain, from the left side 74 



26. Raja nasuta. Roots of the fifth, seventh, and eighth nerves 75 



