CHAPTER XXIII 
TELEOSTEI (CONTINUED): 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 mesocoracoid. 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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