132 ANATOMY OF VERTEBRATES. 



lu this figure the several bones of the head of the European 

 Box-terrapene {Emys Europaa, Wgl.) are represented, disarti- 

 culated, in a side view of their vertebral relations. Beneath the 

 Koman figure, l, are the centrum, i. neurapophysis, 2, neural 

 spine, 3, and parapophysis 4, forming the neural (epencepihalic) 

 arch ; with the pleurapophysis, 5i, and hsemapophysis, 52, forming 

 the hfemal (scapular) arch, with its appendage, of the occipital 

 vertebra. Beneath ii are the centrum, 5, the neurapophysis, 

 6, the neural spine, 7, the parapophysis, 8, forming the neural 

 (mesencephalic) arch : from 8 is suspended by an unossified 

 pleurapojjhysis the hajmapophysis, 40, the hajmal spine, 4i, with 

 the appendage, 47, of the ha?mal (liyoidean) arch of the parietal 

 verteljra. Under iii are the neurapophysis, lO, neural spine, ii, 

 and parapophysis, 12, forming the neural (prosencephalic) arch; 

 with the pleurapophysis, 28, and composite hremapophysis, 29 — 32, 

 forming the hamal (mandibular) arch of the frontal vertel^ra, of 

 which the centrum is not an independent ossification. Beneath 

 IV are, the centrum, 1.3, the connate neurapophvses and neural 

 spines, 14, forming the neural (rhinencephalic) arch ; with the 

 pleurapo])]iysis, 20, hffimapophysis, 21, and haemal spine, 22, 

 forming the ha;mal (maxillary) arch of the nasal verteljra. The 

 diverging ap])endages, for the fixation of this hajmal arch are 

 more developed than in Fishes, where it retains more of its 

 typical mobility. Besides the appendage, 24, of the pleurapo- 

 physis, there is now another, extending in two successive 

 segments, 26 and 27, from the hiemapophysis. The splanchnic 

 ossicle, ic', is jwrt of the acoustic organ : the circle of liones, 17, 

 belong to the visual organ. Such are the ' general homologies ' 

 of the bones of the chelonian jiead, in reference to the vertebrate 

 archetype, fig. 21. Compared with bones of the piscine head, 

 fig. 81, previously named and characterised, those of fig. 92 are : — 



1. Basioccipital. 



2. Exoccipital. 



3. Superoccipital. 



4. Paroccipital. 



5. Basisplienoid. 



6. Alisphenoid. 



7. Parietal. 



8. Mastoid. 



9. Presphcnoid (unossified). 



10. Orbitosphenoid (in great part cartilan-inous). 



11. Frontal. 



12. Postfrontal. 



