ANATOMY OF VERTEBRATES. 133 



13. Vomer. 



14. Prefrontal (with, 15, nasal, distinct in some Chdonia^. 



16. (Petrosal, unossified from an independent centre); if/, a 

 superadded ossicle, ' stapes,' ' columella ' ; witli a gristly represen- 

 tative of ' malleus ; ' in special relation to an organ of hearing affected 

 by viln-ations of air : superadded to all the bones developed in and 

 from the cmlnyonic hiemal arch called ' Meckel's process.' 



17. Sclerotals. 



lit. Tur))inal (unossified). 



20. Palatine. 



21. Maxillary. 



22. Premaxillary. 



24. Pterygoid, with ossification extending into the seat of 23, 

 ento-pterygoid. 



26. Malar (not answering to the bone so numbered in fig. 81). 



27. Squamosal (ib. these bones do not exist in Fislics). 



28. Tympanic (here a single bone ; its subdivisions are 25 — 28 

 in fig. 81). 



29. Articular with )Surangular. 

 29'. Coronal. 



30. Angidar with Splenial. 

 32. Dentary. 



40. Ceratohyal. 



41. Basihyal. 



47. Cerato-branchial, (or ' thyrohyal ' in reference to the 

 larynx of air-breathers, a new developement upon the vestige 

 of the branchial apparatus of fishes). 



50. Suprascapula (unossified). 



51. Scapula. 



52. Coracoid. 



52'. Acromial process of scapula. 



53. Humerus (rarely a separate ossification in Fishes). 



54. Ulna. 



55. Radius. 



56. Carpus. 



57. 53. Digital rays. 



The chief difl:erences in regard to the presence and absence of 

 bones between the Tortoise and the Fish are seen in those 

 belonging to the category of ' diverging appendages : ' thus the 

 ' branchiostegals,' 43, and ' operculars,' 34 — 37, fig. 81, are sup- 

 pressed in the Reptile ; wMle the ' malar,' 26, and squamosal, 

 27, are not developed in the fish. Some minor, but interesting, 

 modifications of cranial structure present themselves within the 



