CLASSIFICATION OF BONES OF THE HEAD. 51 



The Occipital segment ; 

 The Parietal segment ; 

 The Frontal segment ; 

 The Nasal segment. 



EacTi segment consists of a "neural" and a "haemal" arcli. 

 The neural arches are — 



N I. Epencephalic arch (bones Nos. 1, 2, 3, 4): 



N II. Mesencephalic arch (5, 6, 7, 8) ; 



N III. Prosencephalic arch (9, 10, 11, 12); 



N IV. Rhinencephalic arch (13, 14, 15). 



The haemal arches are — 



H I. Scapular arch (50-52) ; 



H II. Hyoidean arch (38-43) ; 



H III. Mandibular arch (28-32) ; 



H IV. Maxillary arch (20-22). 



The diverging appendages of the haemal arches are — 



1. The Pectoral (54-57); 



2. The Branchiostegal (44) ; 



3. The Opercular (34-37) ; 



4. The Pterygoid (23-24). 



The bones or parts of the splanchnoskeleton which 

 are intercalated with or attached to the arches of the true 

 vertebral segments, are — 



The Petrosal (16) or ear-capsule, with the otolites, 16^^; 

 The Sclerotal (17) or eye-capsule ; 

 The Turbinal (19) or nose-capsule ; 

 The Branchial arches ; 

 The Teeth. 



The bones of the dermoskeleton are — 



The Supratemporals ; 

 The Superorbitals ; 

 The Suborbitals ; 

 The Labials. 



Such appears to be the natural classification of the 

 parts which constitute the complex skull of osseous fishes. 



