INTRODUCTION. 11 



Cerato-branchial. 

 Hypo-branchial. 

 Basi-branchial. 

 [Branchial Rays.] 



The remaining branchial arches are successively smaller and their components 

 less regular. The tooth-bearing and gill-less 5th branchial arch is known in Ichthyology 

 as the " inferior pharyngeal bones." 



The ossifications included in square brackets are membrane-bones, whose attachments 

 are approximately represented by their place in the list. 



The membrane-bones of the roof of the skull, representing, apparently, modified 

 scales, can hardly be classified upon any more satisfactory basis than that of mere local 

 relation. A tolerably constant median series consists of a dermo-supra-occipital (flanked on 

 each side by a dermo-epiotic), a pair of parietals, 1 a pair of frontals, 1 and a pair of nasals. 1 

 The orbital ring often, especially in Fishes, yields a more or less complete chain of bones, 

 of which the lachrymal is the most specialised. There may be post-orbital and supra- 

 temporal bones behind the orbit, or a more numerous equivalent series. The maxilla 

 may be connected behind to a jugal, and that again to a quadrato-jugah 



The normal position of various other membrane-bones has been indicated in the 

 preceding table. 



1 These pairs, or some of them, may be consolidated into single bones. 



