CHAPTER XXIII 



TELEOSTEI (COXTIXUED) : ACANTHOPTERYGII OPISTHOMI 



PEDICULATI PLECTOGNATHI 



Sub- Order 10. Acanthopterygii. 



AIR-BLADDER usually without open duct. Opercle well de- 

 veloped ; supraoccipital in contact with the frontals. Pectoral 

 arch suspended from the skull ; no rnesocoracoid. Ventral fins 

 thoracic or jugular, more or less firmly attached to the clavi- 

 cular arch. Gill-opening usually large, in front of the base of 

 the pectoral fin. 



The character from which this sub-order, the most compre- 

 hensive of the whole class, derives its name, viz. the presence of 

 non-articulated, more or less pungent, rays in the dorsal and 

 anal fins, is by no means universal, exceptions to the rule being 

 numerous. The mouth is usually bordered by the premaxil- 

 laries to the exclusion of the maxillaries, and if these should, by 

 exception, enter the oral edge, they are always toothless. The 

 ventral fins are sometimes inserted at some distance behind the 

 base of the pectorals {Haplodactylidae, Platycephalidae], in which 

 case, however, this is due to the elongation of the pelvic bones, 

 which are solidly attached to the clavicular arch. The sub-order 

 is broken up into divisions, which follow in somewhat arbitrary 

 order, the natural affinities being opposed to a linear arrange- 

 ment ; the annexed diagram is intended to remedy this defect. 



SYNOPSIS OF THE DIVISIONS. 



I. No suborbital stay, or process extending from the suborbital bones 

 towards the praeoperculum ; basis cranii double in the symmetrical forms. 



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