PISCES. HOLOCEPHALI. 



65 



Order II. HOLOCEPHALI. 

 This order includes a single suborder only. 

 Suborder. CHIMAEROIDEI. 



These singular fish have the skin smooth and in living 

 forms almost or quite scaleless. The palato-pterygo-quadrate 

 bar and hyomandibular are fused to the cranium, and Meckel's 

 cartilage articulates directly with the part corresponding to the 

 quadrate. The skull is distinctly articulated with the spinal 



10, 



FIG. 5. SKULL OF A MALE Chimaera monstrosa (after HUBBECHT). 



1. nasal capsule. 



2. cartilaginous appendage to 

 the fronto-nasal region. 



3. erectile appendage. 



4. foramen by which the oph- 

 thalmic nerves leave the orbit. 



5. foramen by which the oph- 

 thalmic branch of the Vth nerve 

 enters the orbit. 



6. auditory capsule. 



7. interorbital septum. 



8. mandible articulating with 

 an outgrowth from the posterior 

 part of the palato-pterygo-quadrate. 



9. teeth. 



10. labial cartilage. 

 II. III. V. VII. IX. X. foramina 

 for the passage of cranial nerves. 



column, the notochord is persistent and unconstricted, and the 

 skeletogenous layer shows no trace of metameric segmentation, 



K. 5 



