384 
ACTIXOPTERYGII. 
Suborder IX. ACANTHOPTERYGII. 
Vertebral centra always complete constricted cylinders, none 
modified or coalesced. Snpraoccipital extending forwards between 
the reduced parietals ; squamosal rudimentary and fused with the 
large pterotic; premaxilla always excluding maxilla from upper 
border of mouth; mandible simple, each ramus consisting of not 
more than two elements (dentary and articulo-angular). Pectoral 
arch suspended from cranium; precoracoid arch absent; no infra- 
clavicular plates; pectoral fin with not more than four or five 
basals. Pelvic fin-supports in contact with clavicle, and fins thus 
thoracic or jugular; each pelvic fin usually with an anterior spine 
and five (rarely six to eight) articulated and divided rays. Dorsal 
and anal fins usualJy more or less spinous anteriorly. In the living 
forms :—air-bladder closed, without pneumatic duct, in the adult 
(physoclistous); optic nerves decussating ; intestine without spiral 
valve. 
Division A. BEPYCIFOPMES. 
Pelvic fins thoracic, usually Avith more than five articulated rays 
in addition to the spine. Xo bony stay between circumorbital 
ring and preoperculum. 
Synopsis of Families. 
Head with extensive superficial caAfities for 
mucus ; premaxillse protractile ; lateral 
line conspicuous. Behycid^ (p. 384). 
Head with superficial cavities for mucus; 
premaxillse not protractile; lateral line 
inconspicuous. Aphredodeeid.e (p. 416). 
Head A\ithout superficial caAuties for mucus ; 
premaxillse protractile; lateral line in¬ 
conspicuous . Cyttid^ (p. 417). 
Family DEHYCIDJE. 
Head-bones more or less ridged, thus forming extensive cavities 
which are filled with mucus in the living fish; premaxillse pro¬ 
tractile, and dentition usually feeble. Branchiostegal rays 7 or 8 
in number. Vertebrae from 24 to 30 in number; the posterior 
abdominal centra with downwardly bent transverse processes. 
Pelvic fins (unless rudimentary) with one spine and more than five 
