ANATOMY OF VERTEBRATES. 133 



13. Vomer. 



14. Prefrontal (with, 15, nasal, distinct in some Chelonid). 



16. (Petrosal, unossified from an independent centre); ig', a 

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

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

 by vibrations of air : superadded to all the bones developed in and 

 from the embryonic haemal arch called ' Meckel's process.' 



1 7. Sclerotals. 



19. Turbinal (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. Scpiamosal (ib. these bones do not exist in Fishes). 



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

 in fig. 81). 



29. Articular with Surangular. 

 29'. Coronal. 



so. Angular 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. 58. Digital rays. 



The chief differences 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 ; while the * malar,' 26, and squamosal, 

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

 modifications of cranial structure present themselves within the 



